ARGH!!! I have been having the worst time trying to install Microsoft SQL Server 2005 on my development machine at home. Since I had already been burned in the BETA initiation when I installed at work, I already knew to uninstall any .Net 2.0 development software before I began installation (BETA or not).
This time I was met with a HUGE surprise though. Although I had uninstalled everything that Microsoft's web site told us all to, the install of SQL Server 2005 kept telling me otherwise. Even their BETA uninstall tool was not functioning. The newest version would not complete the uninstall due to an XML error, and the one I downloaded with the BETA software many moons ago would just not complete the uninstall, thinking that I was not logged on as an Administrator. Microsoft really screwed us on this one! There should have been a much easier upgrade path from the BETA versions to the release versions of Visual Studio 2005 and SQL Server 2005.
I even went through the hassle of uninstalling my latest MDAC as one forum suggested. Ugh!
After much Googling, I finally found the answer here:
For some reason, Windows sometimes keeps Windows Installation information intact even when you uninstall software. I am using Windows 2000, so I am not sure if this would also be the case with XP. My development machine at work is XP and had a similar problem, but I did not need this tool to sort it out. The link above leads you to the tool that fixes the install information problem. However, be careful with it. It can mess you up if you are not paying attention.
This is a valuable piece of trial and error that I hope gets you out of hot water! :) Enjoy!