This is from an AI output.
1. The Immediate Fix: End the Windows Installer Process
This is the most common and effective solution. The msiexec.exe process is the Windows Installer, and if it's stuck, it will block any new installations.
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Open Task Manager: Press Ctrl + Shift + Esc (a quick shortcut) or Ctrl + Alt + Del and then select "Task Manager".
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Find the msiexec.exe process: Go to the "Details" tab. Look for any process named msiexec.exe or "Windows Installer". There might be more than one.
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End the task: Right-click on each msiexec.exe process and select "End task".
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Restart the Mathcad installer: Now, try running the Mathcad Prime installer again. It should be able to start.
2. The Deeper Dive: Re-register the Windows Installer
If the previous step doesn't work, the Windows Installer service itself might be in a bad state. Re-registering it can reset it.
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Open Command Prompt as an administrator:
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Unregister the installer: In the Command Prompt, type msiexec /unreg and press Enter. (Note the space between msiexec and /unreg).
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Register the installer: Now, type msiexec /regserver and press Enter.
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Restart your computer: After running these commands, restart your PC. This is an important step to ensure the changes take effect.
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Try the installation again: After the restart, run the Mathcad Prime installer.
3. Check the Windows Registry (Advanced)
This is a more advanced step and should be done with caution. Always back up your registry before making any changes.
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Open the Registry Editor: Press Windows key + R, type regedit, and press Enter.
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Navigate to the key: Go to HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Installer.
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Look for the "InProgress" key: In the left-hand pane, look for a subkey called InProgress under Installer. This key is created when an installation is in progress and should be deleted when it's finished. A stuck installation can leave it behind.
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Delete the InProgress key: If you find the InProgress key, right-click on it and select "Delete". Confirm the deletion.
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Restart your computer: Restart your PC and try the Mathcad installation again.
4. Clean Boot (To isolate conflicts)
This is a good way to see if another program is interfering with the installation.
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Open System Configuration: Press Windows key + R, type msconfig, and press Enter.
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Go to the Services tab: Check the box that says "Hide all Microsoft services".
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Disable all non-Microsoft services: Click "Disable all".
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Go to the Startup tab: Click "Open Task Manager". In the Task Manager, disable all startup items.
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Restart your computer: You will be in a "clean boot" environment with only essential Microsoft services running.
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Try the installation: Run the Mathcad Prime installer. If it works, you know that one of the services or startup items you disabled was the culprit.
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Re-enable services: To find the problematic service, you can re-enable them in small groups until the error returns. Then you can narrow it down. Remember to reverse the changes in msconfig when you're done.
5. Check the Installation Location
While less likely to cause this specific error, it's worth noting that a previous user on the PTC Community forums solved a Mathcad installation issue by using a short file path for the installation files. If you downloaded the installer to a folder with a long name or a deeply nested path, try moving it to a simple location like C:\Mathcad_Installer.
6. If all fails Contact PTC Support
