Resolving STEP 7 1739:10 INVALID DRIVE Hardware Error

Problem Details: Startup Failure of SIMATIC Manager

Engineers running SIMATIC Manager 5.5 SP4 on Windows 7 Ultimate 64-bit or similar workstation OSes may see the following dialog when launching the programming environment, when clicking the Open icon in the LAD/FBD/STL/SCL editors, or when loading hardware:

STEP7 Start (1739:10) Hardware error: INVALID DRIVE

The dialog title is rendered as STEP7 Start (1739:10) in the message bar, and the body is the literal string Hardware error: INVALID DRIVE. The error does not come from a PLC, CP, or IM module — the S7 online stack is not involved at this point. It is a Win32 / OS-level error raised by the STEP 7 runtime while it is enumerating local or mapped drives to validate the installation path, registry entries, and project tree before the workbench is displayed.

The same message has been reproduced on:

• SIMATIC Manager STEP 7 V5.5 + SP4 + HF7 environments
• PCS 7 V8.2 (which embeds STEP 7 V5.5)
• Workstations that previously ran STARTER V4.4 and were upgraded to STARTER V4.5
• Workstations that have TIA Portal V14 and SIMOTION SCOUT V4.5 installed side-by-side

The fault blocks any project open, compile, or download operation. It also reappears when the user clicks the toolbar Open button in AWL, SCL, FBD or CFC editors — confirming that the fault is in the file-access layer, not in the project itself.

Decoding Error 1739:10

STEP 7 wraps the underlying Windows error number with a secondary code. The value 1739:10 is a STEP 7 internal error template used by the framework when a Win32 device or volume query returns an unexpected state. The numeric 10 suffix maps to the symbolic string INVALID DRIVE; the prefix 1739 is the Win32 system error code ERROR_UNEXP_NET_ERR in the broadest sense, but in the STEP 7 context the framework has converted a drive-enumeration failure to this internal token.

Sub-code 10 in the same template family is also used for FILE_NOT_FOUND in the safety-program compiler. That cousin error (1739:10 with body Hardware error: FILE_NOT_FOUND) has been confirmed by Siemens Support to be caused by real-time virus scanners intercepting the file system call before STEP 7 can read the source file. The INVALID DRIVE variant shares the same code path and same root-cause family.

Root Cause Analysis

Six reproducible causes have been observed in the field. Each one must be ruled out before declaring a clean fix.

Cause 1 — Drive Letter Reassignment

The most frequent trigger. The STEP 7 installation was performed when the system disk, data partition, or USB-attached volume was mounted under one letter (e.g., D:\); a subsequent repartition, USB key swap, or storage controller replacement reassigned the volume to a different letter (e.g., E:\). Registry keys under HKLM\SOFTWARE\Siemens\AUTSW\STEP7 and HKLM\SOFTWARE\Wow6432Node\Siemens\AUTSW still reference the old letter, so the framework cannot resolve \Device\HarddiskVolumeX to a valid logical drive and raises INVALID DRIVE.

Cause 2 — Real-Time Anti-Virus or EDR Driver

Avira, Kaspersky, McAfee Endpoint, Trend Micro, Windows Defender Real-Time Protection, and similar products inject filter drivers (Avirfp.sys, mfefirek.sys, tmactmon.sys) on top of the file-system stack. When STEP 7 calls QueryDosDevice or GetVolumeInformation, the filter driver returns a STATUS that the STEP 7 framework interprets as an invalid volume. The companion FILE_NOT_FOUND fault has the same origin and was confirmed by Siemens Support to be caused by the virus scanner.

Cause 3 — Missing or Disconnected Mapped Network Drive

STEP 7 resolves project paths through the SUBST command, the Windows shell namespace, and WNetAddConnection2 entries. If the user previously mapped a UNC path (e.g., \server\step7libs) to a drive letter and that share is offline at logon, the framework aborts enumeration with INVALID DRIVE even when the project itself sits on a local SSD.

Cause 4 — Corrupted STEP 7 Installation

Repair install and in-place upgrade do not always rewrite the registry hive and the aclib.mdb Access database. A partial install leaves the framework in a state where it can launch s7winsfx.exe but cannot resolve the drive table.

Cause 5 — Third-Party Add-On Conflict (STARTER, SCOUT, TIA)

Upgrading STARTER V4.4 → V4.5, installing SIMOTION SCOUT V4.5, or installing TIA Portal V14 modifies the same registry tree. STARTER and SCOUT write under HKLM\SOFTWARE\Siemens\SINAMICS and HKLM\SOFTWARE\Siemens\SIMOTION; TIA V14 writes under HKLM\SOFTWARE\Siemens\Automation\Portal\V14. If two products write overlapping GUIDs or path substitution entries, STEP 7 V5.5 reads the wrong drive table and raises the fault at startup.

Cause 6 — Corrupted User Profile / Temp Folder

The %TEMP% folder or the per-user AppData\Local\Siemens cache can be redirected to a volume that no longer exists (typical after a roaming profile reset). STEP 7 V5.5 expects %LOCALAPPDATA%\Siemens\Automation to be writable; if the path is unmapped, the start sequence throws INVALID DRIVE.

Diagnostic Procedure

Walk the matrix below in order. Each step has a one-line verification that decides whether to proceed to the next cause.

1. Capture system event log. Open eventvwr.msc → Windows Logs → Application. Filter on source Application Error and s7winsfx.exe from the time of the failure. Note the Faulting module name — typically acdll.dll or s7epaapi.dll. If the faulting module is the filter driver of an AV product, jump to Cause 2 immediately.
2. List all volumes. Run wmic logicaldisk get caption,drivetype,volumename,filesystem in an elevated CMD. Verify every drive letter that was present at install time is still present. If a letter is missing, jump to Cause 1.
3. Check mapped drives. Run net use in CMD. Every persistent mapping should resolve. Failed mappings point to Cause 3.
4. Verify temp path. Run echo %TEMP% and echo %LOCALAPPDATA%. Both must resolve to a writable NTFS volume. If either is empty or points to a UNC path that is offline, jump to Cause 6.
5. Check registry. Open regedit and inspect HKLM\SOFTWARE\Siemens\AUTSW\STEP7. The value InstallationPath must exist and must point to a valid directory. Any reference to a drive letter that is no longer mounted is a defect.
6. Review installed packages. Open Control Panel → Programs and Features and sort by Publisher = Siemens AG. Confirm there is exactly one STEP 7 entry, exactly one entry per installed add-on, and no orphan entries with no install path. Duplicates point to Cause 5.

Solution A — Realign Drive Letters

1. Open Disk Management (diskmgmt.msc).
2. Right-click the volume that was originally D:\ and choose Change Drive Letter and Paths….
3. Click Change and assign the original letter. Acknowledge the warning that some programs may stop working — STEP 7 is exactly the program that will resume working.
4. If the original letter is taken by a different volume, reassign the foreign volume to a free letter first, then bring the original volume back to its native letter.
5. Reboot. Launch SIMATIC Manager.
6. Verification: the INVALID DRIVE dialog does not appear. The project tree populates within five seconds.

Solution B — Uninstall STEP 7 per the Official Siemens Procedure

The standard Programs and Features uninstall is not enough — registry hives and the aclib.mdb catalog survive it. Use the Siemens-procedure link from the official support portal:

1. Download and review the official Siemens uninstall FAQ: How do you completely uninstall STEP 7 including all software packages?
2. Stop every Siemens service: sc stop s7oie_srvx, sc stop s7hspsvx, sc stop simatic_net.
3. Remove all entries in Programs and Features for Siemens in the order Add-Ons → STEP 7 → Automation License Manager.
4. Delete residual folders: C:\Program Files (x86)\Siemens, C:\Program Files\Siemens, %ProgramData%\Siemens, %LOCALAPPDATA%\Siemens.
5. Export and then delete the registry tree HKLM\SOFTWARE\Siemens\AUTSW and its 32-bit mirror under Wow6432Node.
6. Delete HKCR\CLSID entries that reference Siemens.STEP7.* and Siemens.Automation.*.
7. Reboot into Safe Mode and confirm no s7*.dll or s7*.exe is loaded by tasklist /m.
8. Reboot back to normal mode and reinstall SIMATIC Manager STEP 7 V5.5 + SP4 from the original media or DVD image. Mount the DVD on a local (not network) drive.
9. Verification: start SIMATIC Manager from the Start menu shortcut. The INVALID DRIVE dialog must not appear. Open a sample project and confirm the compiler, hardware catalog, and online interface are all functional.

Solution C — Exclude STEP 7 from Real-Time Anti-Virus

1. Open the AV product console (Windows Security → Virus & threat protection → Manage settings, or the third-party console).
2. Add the following paths to the process exclusion list:
   • C:\Program Files (x86)\Siemens\Automation\**\s7winsfx.exe
   • C:\Program Files (x86)\Siemens\Automation\**\s7hspsvx.exe
   • C:\Program Files (x86)\Siemens\Automation\**\s7oie_srvx.exe
   • C:\Program Files (x86)\Siemens\Automation\**\s7epaapi.dll
3. Add the following paths to the folder exclusion list:
   • C:\Program Files (x86)\Siemens\Automation
   • C:\Program Files (x86)\Siemens\SIMATIC
   • The folder that contains your STEP 7 project (*.s7p, *.s7l).
   • %LOCALAPPDATA%\Siemens
   • %ProgramData%\Siemens
4. Disable the real-time file-system filter driver entirely as a test, restart, and launch SIMATIC Manager.
5. Verification: if the error disappears with the AV driver disabled, add the exclusions above and re-enable the AV. The error must remain gone.

Solution D — Repair Mapped Network Drives

1. Open This PC → Map network drive.
2. Reconnect every UNC path that was persistent at logon and tick Reconnect at sign-in.
3. Confirm net use shows OK for each mapping.
4. Launch SIMATIC Manager. If the error persists, the UNC path is irrelevant — proceed to Solution B.

Solution E — Reset User Profile and Temp Paths

1. Open System Properties → Advanced → Environment Variables.
2. Reset TEMP, TMP, and LOCALAPPDATA to default system values under %SystemRoot%\Temp and %SystemDrive%\Users\<user>\AppData\Local.
3. Delete %LOCALAPPDATA%\Siemens\Automation\logfiles and %LOCALAPPDATA%\Siemens\Automation\* cache.
4. Log out and log back in (do not restart the machine — the logon must rebuild the profile).
5. Launch SIMATIC Manager.

Solution F — Address STARTER / SCOUT / TIA Side-by-Side Conflict

When STARTER V4.5 or SIMOTION SCOUT V4.5 is installed alongside STEP 7 V5.5, the SIMATIC and SIMOTION registry trees overlap. Remove the conflict with this sequence:

1. Uninstall SIMOTION SCOUT V4.5 via Programs and Features.
2. Downgrade STARTER V4.5 to STARTER V4.4 if the V4.4 installer is available; otherwise uninstall STARTER entirely.
3. Repair the STEP 7 V5.5 installation: Control Panel → STEP 7 V5.5 → Change → Repair.
4. If TIA Portal V14 is installed, run TIA Portal → Installed software → Repair and re-apply the SIMATIC S7-1200/S7-1500 plugin.
5. Reboot. Launch SIMATIC Manager.

Final Verification

After applying any of the solutions above, run a four-step acceptance test:

1. Launch SIMATIC Manager from the Windows shortcut. The workbench must appear without the INVALID DRIVE dialog.
2. Open an existing *.s7p project. The project tree must load in < 5 seconds and no HW error popup should appear.
3. Click the Open icon in the AWL / SCL / FBD / CFC editor toolbar. The file picker must open without the INVALID DRIVE dialog.
4. From the menu, run PLC → Download on a test project. The download must reach the S7-300/S7-400 target.

If all four steps pass, the workstation is restored. If step 1 still fails, escalate to Siemens Technical Support with the Application Event log, the registry export of HKLM\SOFTWARE\Siemens, and a sfc /scannow report.

Troubleshooting Matrix

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