To uninstall Internet Explorer 8, follow these steps:
1.) close all programs.
2.) click Start, and then click Control Panel.
3,) click Add or Remove Programs and in the list of currently installed programs, click Windows Internet Explorer 8, and then click Remove.
The above step is for XP platform and note if IE 8 is installed on SP 3 than you have to first uninstall SP 3 in order to remove IE 8