If you had a Beta version of Framework 2.0 installed on your machine and are moving to a the RTM version, then you might have some trouble with getting the correct version of mscoree.dll in place. The reason is Microsoft Installer's resilence feature will restore the old version of mscoree.dll in your system directory even if you delete it. To fix this follow the belwo support article from Microsoft.

http://support.microsoft.com/kb/908077