I installed VS 2008 today on my machine. I had a beta on my machine and in my experience with betas i am never able to uninstall them easily.
To upgrade from VS2005 beta to actual release was a pain and i had to actually struggle for hours before i got it right.
However it was simpler for visual studio 2008.
Just follow the instructions on link http://blogs.msdn.com/buckh/archive/2007/11/20/how-to-uninstall-vs-2008-beta-2-before-installing-the-final-version-of-vs-2008.aspx to uninstall the the stuff and you are good to go