It's a terrible problem because you want to help people and folk want FREE HELP. You need an algorithm and fortunately, Microsoft is stopping Win 9x, including ME support. Are you going to fill in the gap with long reboots for free or are you going to charge?
Win 2K is actually for terminals. If the XP, whether it is home, pro, or MCE, is not SP2, tell your cu to upgrade it to SP2 before they call you. Those pirated XP Pro corporate editions are just a world of pain. MCE prior to MCE 2005 are horrible. There is stuff going on now with those prior editions that we are never going to know.
I will digress with MCE 2005. I have a directly from Microsoft install cd that SAYS 2005, but actually it is 2002 or 3. So, since I wanted Xbox 360 magic and dual tuner support, I got 2005 off the Internet, except is was pirated and I ratted to Microsoft and even got my money back. So then I got what I wanted from Tiger Direct with a lovely Microsoft remote control, which I have put on my Atlantic Georgia 3250 cable box and it works!
Let me share, that last sentance is nothing less than miraculous. The Tiger Direct is the same old 2005 labeled CD, installed as earlier version, but then there is a bizarre third CD that upgrades to MCE 2005, but does not admit it in system properties.
If it is Win 2K pro less than sp3, just say, "No." If it is XP and less than SP2, just say, "No." And otherwise, bill by the nanosecond.
You want to build you customer base? Tell them the truth.