Resolving TIA Portal V17 Installation Stuck at ClassicCompPrepare

Problem Overview

When a developer uninstalls TIA Portal V18 from a workstation with the intent of downgrading to TIA Portal V17, the V17 setup frequently halts at the ClassicCompPrepare stage and refuses to advance. The installer window remains open, the progress bar stops moving, and the log shows the phase string "ClassicCompPrepare" indefinitely. The V18 uninstaller reports success, but the V17 install cannot complete its compatibility-component preparation, leaving the engineer with no working engineering environment.

This issue is well-known to Siemens Industry Online Support. The most common workaround is a full clean uninstall of the TIA Portal stack, manual cleanup of residual SQL Server instances, .NET assemblies, and Windows Installer staging data, followed by a reboot and a fresh V17 install. Siemens recommends using the SIMATIC Assessment Suite – Data Collector (SAS-DC) to capture system diagnostics and submit them through a Support Request when manual recovery fails.

Symptoms and Error Description

Engineers typically observe the following sequence:

1. TIA Portal V18 is removed via Settings → Apps → Installed apps → SIMATIC TIA Portal V18 → Uninstall, or by launching the V18 setup and selecting Uninstall. The uninstaller finishes without error.
2. The workstation is rebooted.
3. The TIA Portal V17 setup (full installer or update installer) is launched. The user accepts the license, the product selection step, and the security/integrity check.
4. The setup enters the ClassicCompPrepare phase. The phase does not advance for 20 minutes or longer; the setup is effectively frozen. No error code is displayed; CPU and disk I/O are near zero.
5. Killing the setup process (Setup.exe) and restarting it reproduces the same hang.
6. Reinstalling SQL Server 2019 (which TIA Portal V17 uses for project libraries and global libraries) does not clear the issue.

The ClassicCompPrepare phase is the setup routine that prepares the Classic STEP 7 compatibility layer. It registers the legacy WinCC, STEP 7 V5.x, and the SIMATIC Manager redirection components, and it stages the corresponding .NET assemblies and COM type libraries. If any of these targets are partially installed, locked by a hung process, or referenced in the Windows Installer database in an inconsistent state, the phase does not terminate.

Root Cause Analysis

The TIA Portal V18 uninstaller is not fully transactional. When V18 is removed, several shared components are left in an intermediate state because V17 expects a different version of those components. The V17 setup then attempts to transition the shared components from V18 staging back to V17 staging, and the transition deadlocks.

Siemens documents this scenario under the general guidance for Starting to uninstall – TIA Portal, where the integrity check during uninstall is explicitly called out as a phase that can fail when shared components are corrupt. The same logic applies in reverse during a downgrade install.

Pre-Cleanup Prerequisites

Before executing the cleanup procedure, capture the following so that the work can be reverted if necessary:

1. System snapshot / restore point. Create a Windows restore point: Start → Recovery → Open System Restore → Create a restore point.
2. SAS-DC diagnostic bundle. Download and run the SIMATIC Assessment Suite – Data Collector (SAS-DC). It packages installed software, Windows event logs, registry hives, and SQL Server instance state. The bundle is the first artifact Siemens Support requests.
3. Project backup. Copy the %USERPROFILE%\Documents\Automation directory to an external drive. This is the default TIA Portal V17/V18 project location.
4. Authorization/license export. Open the Automation License Manager in the currently working TIA Portal (if any) and export all .liczip files.
5. Local admin account. The cleanup requires local Administrator rights; do not run from a domain user with delegated rights only.

Step-by-Step Resolution

Execute the following steps in order. Do not skip the verification at the end of each step.

Step 1 – Uninstall TIA Portal V18 (if not already done)

Launch the V18 setup with elevated rights, select Uninstall, and follow the prompts. According to the TIA Portal V21 installation guide, the integrity check inside the uninstaller must complete cleanly. If the integrity check itself fails, capture the _SetupLog.txt from C:\ProgramData\Siemens\Automation\Setup\Logs and proceed directly to Step 3 (manual cleanup).

Step 2 – Remove all TIA Portal installations via the inventory tool

Siemens historically provides an inventory cleanup script (the legacy Siemens TIA Portal Cleanup Tool referenced in the Siemens Industry Online Support knowledge base). Use it to enumerate all SIMATIC packages:

1. Open Control Panel → Programs and Features and uninstall, in this exact order:
   1. SIMATIC TIA Portal V18 (and all updates)
   2. SIMATIC STEP 7 Professional V18
   3. SIMATIC WinCC Professional V18
   4. SIMATIC S7-PLCSIM V18
   5. SIMATIC Visualization Architect V18
   6. Startdrive V18
   7. SINAMICS Startdrive V18
2. Reboot.

Step 3 – Clean up SQL Server instances

TIA Portal V17/V18 each create a SIEMENS-prefixed SQL Server instance. Downgrade conflicts often originate here.

1. Open SQL Server Configuration Manager.
2. Stop services SQL Server (SIEMENS) and SQL Server Agent (SIEMENS) if present.
3. Open a command prompt as Administrator and execute:

   sc delete "MSSQL$SIEMENS"
   sc delete "SQLAgent$SIEMENS"
   

4. Delete the data directories:

   rd /s /q "C:\Program Files\Microsoft SQL Server\MSSQL15.SIEMENS"
   rd /s /q "C:\Program Files (x86)\Microsoft SQL Server\MSSQL15.SIEMENS"
   

5. Reboot.

Step 4 – Clear Windows Installer staging

1. Stop the msiserver service: net stop msiserver.
2. Delete orphaned MSP/MSI files in %WINDIR%\Installer that reference "Siemens" or "SIMATIC" (do not delete the $PatchCache$ subfolder).
3. Run msizap G !{GUID} for any TIA Portal product code that still appears in the registry under HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall and HKLM\SOFTWARE\WOW6432Node\Microsoft\Windows\CurrentVersion\Uninstall.
4. Restart the service: net start msiserver.

Step 5 – Remove .NET and Visual C++ residues

1. Open Apps & features, sort by publisher, and remove all entries from Siemens AG and Microsoft Corporation whose names start with Microsoft .NET or Microsoft Visual C++ and that have a version higher than what TIA Portal V17 supports (V17 requires .NET Framework 4.8, VC++ 2015–2022 14.20+).
2. Run the .NET Repair Tool:

   dotnet --list-runtimes
   

   Note the runtimes; V17 is compatible with .NET Desktop Runtime 6.0.x and 7.0.x. Uninstall 8.0 preview channels, which V18 sometimes registers and V17 rejects.
3. Reboot.

Step 6 – Clean residual directories and registry

1. Delete the following folders if they exist:
   • C:\Program Files\Siemens\Automation
   • C:\Program Files (x86)\Siemens\Automation
   • C:\ProgramData\Siemens\Automation
   • C:\Users\<user>\AppData\Local\Siemens\Automation
   • C:\Users\<user>\AppData\Roaming\Siemens\Automation
2. Delete registry keys:

   reg delete "HKLM\SOFTWARE\Siemens" /f
   reg delete "HKLM\SOFTWARE\WOW6432Node\Siemens" /f
   reg delete "HKCU\SOFTWARE\Siemens" /f
   

Step 7 – Disable antivirus and EDR

Real-time scanning of %TEMP% and %ProgramData%\Siemens is a frequent cause of ClassicCompPrepare hang. Temporarily disable third-party EDR (CrowdStrike, SentinelOne, Defender for Endpoint) and Windows Defender real-time protection. Re-enable after the install.

Step 8 – Install TIA Portal V17

1. Insert the V17 DVD or mount the SIMATIC_TIA_PORTAL_STEP_7_PROF_V17.iso.
2. Right-click Start.exe → Run as administrator.
3. Select Install, choose the products (TIA Portal, STEP 7 Professional, WinCC Professional, S7-PLCSIM, Startdrive), and accept the license terms.
4. Monitor the ClassicCompPrepare phase; under a clean state it should complete in 5–15 minutes on a modern workstation.

Step 9 – Apply the latest V17 update

After the base install completes, apply the latest update (currently V17.0 Update 5) by launching the Setup.exe of the update package. This restores the WinCC comfort panel migration tables and the SINAMICS Startdrive V17 catalog.

Verification Steps

After the install completes, perform the following checks before declaring the workstation healthy:

1. Launch TIA Portal V17. Open Start → Siemens Automation → TIA Portal V17. The splash screen should display V17.0 Update 5 (or the update applied).
2. Open a sample project. Create a new project, add an S7-1500 CPU, and save. Close and re-open to confirm the project database commits to the SIEMENS SQL instance.
3. Check installed software list. In Apps & features, confirm the following products are present and no V18 product is listed: SIMATIC TIA Portal V17.0, STEP 7 Professional V17.0, WinCC Professional V17.0, S7-PLCSIM V17.0, Startdrive V17.0.
4. Validate licensing. Open the Automation License Manager and confirm the local license is detected. If it is not, re-import the .liczip backup from Pre-Cleanup Step 4.
5. Run a compile cycle. Open the S7-1500 project, add a simple FB in ladder, compile (hardware + software), and verify no warnings appear in the compile log.
6. Inspect Windows event log. Open Event Viewer → Windows Logs → Application and filter by source MsiInstaller. The last 10 minutes should show successful install events; no 1001 .NET Runtime errors or 1022 SQL Server errors should be present.

Prevention and Best Practices

To avoid the ClassicCompPrepare hang on future version changes, observe these practices:

• Do not skip major versions. If you need both V17 and V18, install V17 first, then install V18 alongside it. Siemens supports parallel installation of TIA Portal V17 and V18 on the same workstation as long as they are installed in this order.
• Avoid in-place downgrade. The downgrade path V18 → V17 is not officially supported; always uninstall V18 and reinstall V17 as two discrete transactions separated by a reboot.
• Maintain a golden image. Image the workstation after a clean V17 install using a tool such as Acronis, Veeam, or Windows DISM capture. Restore the image for the next downgrade rather than walking through the manual cleanup.
• Patch Windows first. Run Windows Update and install all .NET Framework cumulative updates before installing TIA Portal. The V17 setup relies on the latest servicing stack.
• Keep an offline package store. Maintain the V17 base DVD and the latest V17 update ISO in a known network share. Network installs that fetch files on demand can stall when antivirus sandboxes the payload.
• Document the SQL instance name. TIA Portal V17 uses SCC and SIEMENS SQL instances. Record the names so that future migrations do not orphan them.

When to Escalate to Siemens Support

If the V17 setup still hangs at ClassicCompPrepare after the manual cleanup, escalate. Open a Support Request at the Siemens Industry Online Support portal. Attach the SAS-DC bundle captured in Pre-Cleanup Step 2, plus the most recent _SetupLog.txt from %ProgramData%\Siemens\Automation\Setup\Logs. Mention "ClassicCompPrepare" verbatim in the subject; Siemens routing rules map that phase name to the TIA Portal setup team. The Support Request is a no-cost engagement for active license holders.

Alternative: Reinstall Windows

If the workstation hosts mission-critical projects and downtime is cheaper than debug time, a full Windows reinstall is the fastest path to a clean V17. The expected timeline is:

1. Image backup: 30 minutes
2. Windows 10/11 clean install + drivers: 60 minutes
3. TIA Portal V17 base install: 30 minutes
4. V17 Update 5 install: 20 minutes
5. Project import and compile validation: 30 minutes

Total: approximately 3 hours. Compare this with the 2–4 hours of manual cleanup and the residual risk that some registry key was missed.