I just upgraded to Windows 7 RC1 from the Win 7 beta. In the beta I had the Adobe Creative Suite CS2 installed. Everything worked fine but as I recalled during the install, it barfed on the "(x86)" part of the install path.
Last time I simply removed the parenthesis and everything worked fine. This time I thought I'd be clever and just remove everything just leaving, "C:\Program Files". That was my mistake.
Under 64bit Windows, the OS is expecting 64bit applications to be installed under Program Files and 32bit applications to be installed under Program Files (x86). Since CS2 is 32bit only, it royally borked my install, forcing me to completely uninstall and reinstall. This time I'll install into "C:\Program Files x86" which will work just fine.
Lesson learned? Don't install 32bit applications into the 64bit Program Files folder.