There's a couple of programs worth mentioning here, especially if you want to get older DOS games working.
http://dosbox.sourceforge.net/news.php?show_news=1
Runs a virtual machine with a DOS style layer, perfect for running most of your old games.
also
http://www.scummvm.com/
is a replacement game engine for SCUMM based games and will play older Lucasarts based SCUMM games as well as Broken Sword 1 & 2. Monkey Island 1 and 2 works a treat on it with full sound, didnt crash once.