Vista - Internet Explorer 8 won't install on my vista 32bit ulitmate

Hi all. I just found this forum and I need some help. I'm having trouble installing IE 8. I'm running vista ultimate 32bit and my pc is a custom build. I also have xp pro, and windows 7 build 7000 all on the same PC but each OS on different drives. I'm using AVG 8.5 anti virus/firewall with the vista.

My problem is before IE 8 came out my IE 7 got corrupted somehow and I had to reset it in order to get it to work again. The next day I think IE 8 came out and I was not able to install and I have tried several time to install it. It works fine on my xp pro. I have not had any issues with that OS just with vista. Any help would be great or tips. I really dont want to do a clean install with vista only if worst come to worst. Thanks.