Usually error 1721 occurs when you try to uninstall a program, but it can be fixed using a couple commands and the command prompt
- Tip: Keep hitting F8 repeatedly after your computer starts – depending on your motherboard a different key may also work, read your motherboard manual!
Steps fix error 1721
1. Step Restart your computer and press “F8” on your keyboard before Windows starts up. Then select the option “Safe Mode” and press enter. Make sure you are logged on with your administrator account.
2. Step Next, type msiexec /unregister into the command prompt and press the Enter key.
3. StepAgain type msiexec /regserver into the command prompt and press the Enter key.
4. Step Finally type ‘exit’ and press Enter. That are the complete steps to fix Windows 7 error 1721.
It is also a good idea to run the Windows file checker utility by entering this command: