I cleaned up my hard drive several weeks ago.  One task that I accomplished was removing a splattering of Windows SDK installations.  I think I had six different versions installed.  It certainly felt good and freed up some disk spaced consolidating everything to Windows SDK 7.1.

Except, I tried to build a setup package of a program I had completed.  It would not builld.  Both VS 2010 and VS 2008 informed me that it could not find the msi installer AND the WindowsSDKDir was pointing to an invalid location.  Hmm...

Not to fear.  I did a repair of VS 2008 and VS 2010 and all is well.

One thing I did learn, do not repair VS 2008 SP1 from the installation media: "Do not repair VS 2008 SP1 from installation media".  I followed the same logic when repairing VS 2010.  Repair the systems from the Add-Remove programs menu item (when using XP.)

Unfortunately, I am back to 3 installed versions of the Windows SDK, but that's OK.  Everything is working now and I am not going to mess with it.