The Underscore Archives

I didn't think this was going to  be possible but it looks as though a group
of programmers are trying to achieve this.

http://www.fallingleafsystems.com/

Its still in its early stages but they do claim that XP'ers will soon be
able to play Halo 2 and Shadowrun once they have sorted out the API's and
other coding.

Maybe there is hope and no need to use Vista.