because of microsoft's...intelligence...if the install to the .net framework fails it usually wont work when you try and re-install it again and you have to manually remove it and then try again. im not sure if this is the problem, but its possible. here is a link
http://support.microsoft.com/default...b;en-us;320112 on microsofts msdn site that explains how to remove it, however it involves editing the registry and deleting files in your system folder so if you are uncomftorble about doing this then dont, the last thing you want is a messed up windows installation.
if you are uncomfortable doing that than the other thing you could try instead is installing the 2.0 beta version of the .net framework. which can be found on microsofts site at this page
http://www.microsoft.com/downloads/d...DisplayLang=en