http://bugs.winehq.org/show_bug.cgi?id=30845
--- Comment #7 from Hans Leidekker hans@meelstraat.net 2012-06-10 14:26:17 CDT --- (In reply to comment #6)
If I create that key, the dotnet20 installer puts up a scary dialog box "A fatal error occurred. However, mscorees.dll could not be loaded to display the appropriate error message.\n\nPlease reinstall the .NET Framework." but installation then continues, and the psdk install starts ok.
It's surprising that it needs that key because I believe it should install on Windows even if no older runtime is present. What happens if you override mscoree and fusion to native only?