This may be a long shot, but I had a similar problem after installing a previous version of the .NET Framework from Windows Update, that wouldn't pick up as an old version when the newest patch of .NET was released. This happened on 4 different systems, 3 running WinXP Home, 1 running WinXP Pro, and all of them different physical builds. If you have .NET Framework 1.1 installed, you might try uninstalling it, rebooting, then going to Windows Update and downloading it again. Again, this is a long shot, but it may help out.