If you already have IE8 Beta and you tried to install IE8 Beta 2. You might end up getting the following error. ( which was a bit annoying for me)
If you're using Windows Vista, You probably won't find 'Internet Explorer 8 ' under add/remove programs in the control panel. You will instead have to check your updates for IE 8 and remove it.
That done, you can install IE 8 beta 2 like breeze.. :)