So how about,
"If it's a computing device of some sort that isn't made
 anymore, nor is there any commercial support to be had for it. Oh, and if
 the computing device is capable of running Windows 95 or better, it's still
 off topic." 
 That would still exclude many 386s, for one. Even 2K could theoretically run
 on a P133, although that would be clinical evidence of masochism, I think.
 XP wants a 233MHz Pentium-type CPU minimum. I think that would be a more
 reasonable cutoff, if we want a particular Windows version to be the cutoff. 
 
Hit send too fast, there was one other thing I wanted to add: commercial
support is a pretty wide term. Even a IIgs is still "supported" by Apple
insofar as there are tech notes and downloadable software still up on the
website for it, despite the fact that their service department would get a
good chuckle if you ever dropped by asking for a new motherboard. And there
are still companies making hardware for the Commodore 64 in small quantities,
which is still "commercial support" of a sort.
I think using a Windows-based boundary will be firmer and less ambiguous.
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  Cameron Kaiser * Floodgap Systems * 
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-- Now and then innocent people are sent to the legislature. ------------------