Having problems uninstalling previous betas of Whidbey? Try msiinv.exe
If you are having problems trying to uninstall previous betas of Whidbey with little bits and pieces still laying around (and who doesn't have that problem), try out msiinv.exe. This tool seems to help pretty well. Instructions for it are here. This could be helpful if you are trying to install/uninstall beta2, September CTP, October CTP of Sql Server (.NET 40903), November CTP (.NET 41202), or December CTP of Sql Server (.NET 40903.27).
Also, please note that right now, the different teams at Microsoft are each putting out their own CTPs, which almost definitely will not work with each other. Think VPC or VMWare and save yourself the pain and agony.