The Lucas Arts game require
http://www.scummvm.org which is free and runs on windows xp and nearly every other Operating system.
They even have a legal, free version of beneath a steel sky available to download
For other older games, you need a DOS emulator, a widely recommended one is dosbox, which is free and open source (
http://dosbox.sourceforge.net/ )
catcha back on the flipside,
keyshawn