bit of a pain in the ass to download and I'm having some trouble getting online with it but... mechwarrior 4 is now free!
http://battletech.catalystgamelabs.com/2010/04/30/mechwarrior-4-free-release-available/
http://battletech.catalystgamelabs.com/2010/04/30/mechwarrior-4-free-release-available/