How to do a clean reinstall of MDT?

Summary

After installing or updating MDT, errors such as "Unknown command", "File not found", "Failed to find the dynamic link library" may appear, or the program's own self-diagnosis may report "Errors have been found in the program installation". In the vast majority of cases the cause is a damaged or incomplete installation — usually because the antivirus or the firewall blocked the copying of some files — and it is solved with a completely clean reinstall: uninstall, temporarily disable the antivirus, download the installer again, extract it fully and install as administrator.

Applies to

• MDT — applies to MDT 9, MDT 25 and MDT 26 (versions documented in the support cases; for MDT26, the installation manual also states that MDT9, MDT25 and MDT26 can coexist on the same computer)

• CAD: AutoCAD, ZWCAD, BricsCAD, GstarCAD (cases documented with AutoCAD 2020–2025, ZWCAD 2020 and 2023–2026, BricsCAD 25 and GstarCAD 2025)

• Windows 10 and 11

Symptoms

• When running any MDT command: Command "MDT25_..." unknown. Press F1 for help (or Unable to recognize command ...).

• Messages such as Failed to find the desired dynamic link library or other files referring to modules like Puntos25.ZRX, Sup25.ZRX, sup25.arx, etc.

• The MDT self-diagnosis generates a file listing "Files not loaded" or "Missing files" together with the text "Errors have been found in the program installation".

• The MDT menu or ribbon does not appear after installation, or only the one belonging to another installed version appears.

• "File X not found" messages when using a particular command (for example Aplitop.App.Editors.dll, Seccdibujo9.dll, AplitopTLM.dll, mapa9.arx, MDTv5OE.GRX, IfcPSetLibrary24.dll).

• Unable to find a definition for the dialogue box ... or Semantic error(s) in DCL file ... config.dcl.

• If the error is «Class not registered», «Unable to open the file CargadorNet.dll» or «Unknown error 0x80131700», do not reinstall yet: almost always a Windows component is missing (.NET Framework or Visual C++), and that case has its own solution.

• "Invalid pointer" errors when running certain commands.

• The viewers (surfaces, cross sections, long sections...) show "No TcpMDT-CAD license".

• During installation or when opening the program a Windows Security or antivirus warning appears, and from that moment on some commands stop working.

• Error: message (MDT,...) not found (lang=0) after applying a partial update.

Cause

The installation is damaged or incomplete: files are missing or out of date. The documented reasons are:

• The antivirus or firewall blocked, quarantined or deleted files during extraction, installation or afterwards (this is the most frequent cause; some modules are detected as false positives).

• The installation was run without administrator privileges or with the setup launched from inside the ZIP without extracting it completely (which does not work).

• The installer was out of date or corresponded to a build with an error already fixed by Aplitop.

• In MDT26: uninstalling MDT25 after having installed MDT26 may delete shared system files (the System32 folder).

Solution

Most cases are solved with the clean reinstall of the first case. The remaining cases cover specific variants identified by support.

Case: damaged or incomplete installation — clean reinstall

1. Close the CAD and any open projects completely.

2. Uninstall MDT completely from Add/remove programs (Settings > Apps). Uninstall only the version you are going to reinstall: do not uninstall the other major versions installed (MDT9, MDT25 and MDT26 can coexist on the same computer).

3. If you are reinstalling MDT9, check after uninstalling that no file remains in C:\Program Files (x86)\Aplitop\MDT9; if any remains, delete it.

4. Completely disable your antivirus and/or firewall (including third-party ones). If the antivirus deleted the setup itself while extracting, add an exception so that you can continue.

5. Download a fresh copy of the installer corresponding to your license from your private area at private.aplitop.com (in some cases support provides a download link directly).

6. Extract the downloaded ZIP completely. Opening the ZIP and running the setup from inside it does not work.

7. Run the setup as administrator (right-click > Run as administrator).

8. Check that the installer detects your CAD version and finish the installation.

9. Start MDT from the MDT icon and wait for the CAD to start completely (the first time it may take longer).

10. Go to the MDT > About... menu and wait for the screen with the license information to appear.

11. Enable the antivirus again and add an exception for the folder C:\Program Files (x86)\Aplitop to avoid new blocks.

Case: the antivirus has quarantined files

If the program was working and, after a Windows Security or antivirus warning, a particular command stops working ("File not found" or "Unknown command"):

1. Open your antivirus quarantine list and check whether there are blocked MDT files (for example .arx or .dll files from the installation folder).

2. Restore the files and add an exception so that the antivirus does not block them again.

3. If the files have already been deleted or you cannot restore them, carry out the clean reinstall of the previous case.

Case: the downloaded installer had an error already fixed

Some failures do not depend on your computer, but on a one-off error in a particular build of the installer (for example: an error when installing the blocks reporting a corrupt file, a download failure "Downloading installation data from the web has failed", viewers showing "No TcpMDT-CAD license", or incompatibilities between MDT9 and MDT25).

Before writing off the installer as faulty, rule out the cheapest causes: check that you are not running it from inside the ZIP, from a USB drive or from a folder with a very long path, and that you have enough disk space. These are the most frequent reasons for the setup to report a damaged file or to hang while downloading a component. If the path was already short, or if the failure repeats at the same point after correcting it, continue with this case.

In the documented cases, Aplitop fixed the installer and it was enough to:

1. Download the most recent installer again from the private area (or the corrected link provided by support).

2. Uninstall the affected version —only that one, as per the warning in the first case— and install again.

If the error persists after reinstalling with the most recent installer, contact support: it may be an installer problem that has not yet been fixed.

Case: system files missing from System32 (MDT26 after uninstalling MDT25)

In MDT26 there have been cases in which no command works because a couple of system files are not present, usually as a result of having uninstalled MDT25 after installing MDT26 (the uninstall removes shared files) or of an antivirus block. Solution applied by support:

1. Support provides a compressed file with the affected files.

2. Extract it and copy the resulting files into C:\Windows\System32, overwriting if prompted.

3. Start MDT again and run MDT > About TCP-MDT first.

If that does not solve it, run the MDT26 installation again with your installer to restore the deleted files.

Case: a specific file is missing or out of date (support provides it)

When the error identifies a specific file, the support team can send it to you to copy manually into your folder, as a quick alternative to reinstalling. Documented files and folders:

Bear in mind:

• The file depends on the exact version of MDT: in one documented case, the version 9 DLL did not work on 8.5, and a reinstall was needed.

• Before asking for the file, check the antivirus quarantine (previous case): the file is often there.

• For AplitopTLM.dll (templates / inserting images), support solved one case by renaming AplitopTLM.dll to AplitopTLM.old in C:\Program Files (x86)\Aplitop\MDT25\bin\x64, starting MDT25 from its icon and clearing the checkbox in the warning that appears; in another case it was solved by reinstalling with the antivirus disabled. Check with support before applying this change.

• If a particular .arx module does not load (for example StreetView25.arx), support may tell you to load it by hand with the CAD's ARX > Load command, looking for it in the installation folder (e.g. C:\Program Files (x86)\Aplitop\MDT25\r24x64); in the documented case the definitive solution was the clean reinstall.

Case: errors in every command after updating (telemetry)

In one documented case, after an update every command gave an error even though the files were complete; the support team solved it by disabling the application's telemetry. If after a clean reinstall any command still fails, contact Aplitop technical support so that they can check this point through a remote connection.

If the problem persists

• Run MDT > About TCP-MDT, click the Export button and save the generated file: it lets support check the state of the installation.

• If MDT has generated a self-diagnosis file ("Errors have been found in the program installation"), attach it to your incident at https://private.aplitop.com/support/form.

• If you work in a company with IT restrictions (permissions, corporate antivirus), coordinate the installation with your IT department: in the documented cases it was necessary to temporarily disable the protections under their supervision and add exceptions.

• Aplitop technical support can make a remote connection to your computer through the chat at www.aplitop.com to review the installation.

Category: Installation and updating · Level: Basic