How to Fix a 1721 Windows Installer Error

By Greg Lindberg

When using the "Add or Remove Programs" feature in the Windows operating system to remove a program, you may receive "Error 1721." This error indicates that there is a problem with the Windows Installer package. In order to correct this error and be able to remove programs you must re-register the Windows Installer service by using the command prompt feature within Safe mode. This process helps to fix any corrupted files that were a part of Windows Installer.

Step 1

Restart your computer and press the “F8” key on your keyboard before Windows starts up.

Step 2

Press the “down” arrow key on your keyboard to highlight the “Safe Mode” option. Press the “Enter” key on your keyboard.

Step 3

Select your computer with the arrow keys and then press the “Enter” key. Your computer will then start in Safe mode and you’ll be prompted to log in as a local administrator.

Step 4

Click on the “Start” button, then click “Run.” Enter “cmd.exe” into the “Open” field and then click on the “Open” button.

Step 5

Enter “msiexec /unregister” into the command prompt and press the “Enter” key. Enter “msiexec /regserver” into the command prompt and press the “Enter” key.

Step 6

Type “exit” into the command prompt and press the “Enter” key. The Error 1721 will be fixed and you can remove programs using the "Add or Remove Programs" feature.