I was going to donate a HP printer to the arts center I'm volunteering for, but the computer they have right now is a PII-233Mhz machine running Windows98. This turns out to be a sticking point which prevents the printer from being useful to them, as I don't have the original Windows driver CD.
I found out that HP (and I expect most other printer manufacturers) have discontinued support for Windows98 (since July 2007), going so far as to remove all Windows98 printer drivers from their website, not even making them available on an "as-is, no official support" manner. Folks with older computers running Windows98 (that can't run any newer version of Windows) cannot use new printers, even those manufactured prior to July 2007.
Linux, of course, still receives printer driver support from HP and a few other places (and auto-installs HP USB printers without any prompting), so it appears that to donate the HP printer I'm probably going to have to donate Linux as well, either on the existing system or donate a newer computer as well.
(sits back and waits for the inevitable "standards printers are a better choice than driver-based printers" comment from someone... ;-) )