I'm another one asking for Linux support. Shouldn't be too difficult for most old games, and you're giving Vista and XP support already.
mhe: Correct me if I'm wrong, but doesn't Cedega enable virtually any Windows game to run on Linux? If so, Cedega emulates Windows, which runs DOSBox which runs game. A bit complicated, but since hardware performance is not an issue with today's rigs, I'd find that to be a viable solution.
Or you could just use a Linux build of DOSBox, it's cross-platform after all. And several of GOG's adventure games could be run under ScummVM, also cross-platform.
AFAIK Cedega requires you to pay a monthly subscription fee, and not all games are guaranteed to work. Essentially the only major barrier to playing Windows games on Linux is support for recent versions of Direct3D.
mhe: I am a Linux user myself, but over the years I have found it easier to set myself up a second machine with windows exclusively for gaming.
Would if I could, but right now my means won't stretch that far, nor do I have the space to dual-boot.
mhe: Also, you'd probably run into some serious issues with version conflicts etc with all the different distros out there (foo.lib might be another version on Debian than it is on Red Hat etc). The Linux and OSX guys would really have to make this worth CDP's while...
This is very true. If it was me, and if the game was emulated with DOSBox, ScummVM, winelib or whatever, I would just provide .deb and .rpm packages with dependencies on said emulation software, plus a plain .tar.gz zipped installer for any distros which aren't covered by those two package formats, which is not many distros - mainly Slackware "package management is for wusses" and Gentoo "compile everything by hand" hard-liners.