When you are installing and uninstalling software on a Windows computer, you are using the Windows Installer Package. This is a specialized software platform that accommodates moving programs in and out of a PC. Microsoft takes pains to make sure their installer can handle most programs. On the flip side, hundreds of software manufacturers customize their applications to work with Windows.

Where do Errors Come From?

Even with the best intentions though, sometimes an error occurs for no apparent reason. One of those more common errors is the Uninstall Error 1721. As its name suggests, the error is brought about when the Windows Installer has encountered a problem removing a given application.

When you get the message that error 1721 has occurred, there are a few things to try. The first two options are more mild. They try to approach the problem in a way that is easy for the average computer user. If you're a little more adept at PC maintenance, the latter methods may yield some additional success, but be sure to be careful and – if you're not positive what you're doing – get help from a pro.

Try These First

Method 1

Try again. Sometimes it's that simple. Of course, you probably haven't looked for answers without trying a couple of times to no avail. If trying again fails. Try the standby: rebooting your computer. This will often clear temporary caches that could contain residual data that, in turn, is interfering with the uninstall process. If that fails try a third-party uninstaller.

Method 2

An installer does more than just delete a program's icon and it's running .exe process. It goes into the PC and removes dependent resources and adjusts settings in a way that protects your computer's integrity. Several vendors make a good uinstallations applications; one free application that is frequently recommended is the Revo Unistaller. http://www.revouninstaller.com/

Advanced Fixes

Advanced Method 1: Register the Windows Installer Package

• Restart your computer in safe mode

  • During the reboot, your BIOS information is displayed (that page that says custom set up F1)

  • Press F8

  • Select safe mode by highlighting it with the arrow keys and press enter.

• Log into the administrator account

• Open the main menu and click on run

  • Enter cmd.exe

  • Click on OK

• That opened the command prompt window

  • Give the command msiexec/unregister and enter

  • Give the command msiexec/register and enter

  • Give the command exit and enter (closed command prompt)

• Return to add/remove programs and remove the desired program from there.

Advanced Method 2: System File Checker

• Open command prompt

  • Open main menu

  • Select run

  • Enter cmd.exe

  • Click OK

Before going further, be sure to have the installation disks to your version of Windows, you may be prompted to provide them.

• Give the command sfc/purgecache and press enter

• Let computer run, may take several minutes and please follow any prompts you may get

• When completed, Windows will notify you that the changes were successful.

• Give the command sfc/scannow and press enter.

• Let computer run, which may take several minutes and please follow any prompts

• When computer is finished, give command exit and press enter to close command prompt.

• Continue with uninstalling the program from add/remove programs.