Have a read of this thread at the Officials, a few things in there (install location, running installer as admin etc.) to bear in mind for Morrowind and Windows OSs from Vista onwards. I should note that I've had the GOTY CD since the XP days, and have uninstalled it last year all to get rid of one mod that NMM would not successfully deactivate. I swear, it behaves like all the .esm files were wiped off the disc.