Error 1721 is an error commonly experienced when trying to uninstall a program using the Add or Remove Programs function in Microsoft Windows XP.
This error generates a pop-up message identifying it as Error 1721. It explains that the problem is caused by an error with the Windows Installer package. This often means that a program needed for the removal of the program was not installed with the software. The message will also advise the user to contact the developer or distributor of the program they are trying to uninstall.
How to Solve the Problem
To solve Error 1721, you need to perform the steps in re-registering the Windows Installer service. If the problem persists, you can run a System File Checker.
Re-registering Windows Installer Service
If the Microsoft installation engine is internally corrupted or is experiencing malfunctions, you will not be able to remove any of the programs installed by the Windows Installer.
When an Error 1721 occurs, it is important to unregister and then re-register the Windows Installer service to correct the corrupted parts of the engine. This can be carried out through the following steps:
1. Start your computer in Safe mode. To do this:
a. Restart the computer.
b. After the BIOS information is displayed, press F8 repeatedly until you are presented the Safe Mode option.
c. Select Safe Mode and Enter.
d. Select your computer and Enter.
2. Log on to the computer as local administrator.
3. From the Start menu, select the Run option.
4. In the pop up box, type CMD.EXE then click OK.
5. Type misexec/unregister at the prompt. Press Enter to complete the unregister command.
6. At the next prompt, type msiexec/regserver. Press Enter to complete the re-register command.
7. Close the command prompt by typing Exit and pressing Enter.
8. Try to uninstall the application again using the Add or Remove Programs function of the Control Panel.
Running a System File Checker
Sfc.exe or the System File Checker is intended to scan protected Operating System files. This validates whether it is the right version or not. It has the capacity of detecting corrupt files or incorrect versions then replacing them with the correct file from the Windows installation source files.
This can be accomplished by performing the following steps:
- From the Start menu, select the Run option.
- In the pop up box, type CMD.EXE.
- Click OK.
- Type sfc/purgecache in the command prompt then press Enter.
- Now type sfc/scannow and then hit Enter. Note that steps 4 and 5 may require you to provide the Windows installation source files. The full process of running the command line may take several minutes to finish.
- Type Exit then press Enter to safely exit the command prompt.
- Remove the software program.