If you are running Windows XP, click on Start > Run. In the run box, type: %windir%\ie8\spuninst\spuninst.exe
then press ENTER. Click continue, then click OK on the warning message. Regardless of the message, your programs will work fine.

If you are running WIndows Vista, use the following instructions:

1. Carefully select and then copy the following command:
FORFILES /P %WINDIR%\servicing\Packages /M Microsoft-Windows-InternetExplorer-8*.mum /c "cmd /c echo Uninstalling package @fname && start /w pkgmgr /up:@fname /norestart"
2. Click Start, and then type Cmd.exe in the Start Search box.
3. In the list of programs, right-click Cmd.exe, and then click Run as administrator.

Note If you are prompted for an administrator password or for confirmation, type the password, or click Continue.
4. Right-click inside the Administrator: Command Prompt window, and then click Paste to paste the command that you copied in step 1.
5. Press ENTER to uninstall Internet Explorer 8.
6. When the uninstall program is finished, restart your computer.