So here's something interesting. In Windows XP, Vista and 2003, in Add/Remove Programs, there is a listing of installed programs. For many items, there is a size listed as well as a "date lasted used". Wver wonder how it gets that information? Unfortunately, I had to find out because of an incident. I found myself reading Raymond Chens MSDN blog entry alled, appropriately, "How does Add/Remove Programs get the size and other information?" In it, it states that there are only a few mandatory options listed in the registry, one of which is *NOT* the program executable name. If the program executable name is not explicitly listed in the registry, Windows basically starts guessing on information. There is a follow-up blog worth reading called "Why did the Add or Remove Programs control panel try to guess all that information?" if you are curious.
(BTW, this may also be true of W2K machines, but since I don't have ready access to one, and I don't care, I won't claim it for fact. *smirk*)