Which Antivirus?
What is happening when you try and un-install?
Any error messages?
What operating system are you running?
Which Service Pack do you have?
Is your computer switched on?
Which version do you have. Version 7 has several bugs in it apparenty which prevent it updating and slow your PC down. It should have its own uninstall programme, if this is not working, have you tried Add/Remove in Control Panel. Failing these you will have to manually uninstall it piecemeal. http://hacks.oreilly.com/pub/h/670 is a good site to refer to.