ATI originally released had a deal where every owner of an ATI card gets:
HL2 deathmatch and HL2 Lost Coast for free.
nVidia countered by getting those games, and including a DEMO to Peggle Extreme, and extended Portal demo...
Since demos are pretty much worthless, What BOTH companies give you is free HL2 deathmatch and HL2 lost coast (which is a 30 minute microlevel of HL2)...
http://www.steampowered.com/ati_offer1a/
Note, you don't have to create a new account, you can associate those games with your existing account... and this "limited time offer" has been going on for more then a year now.
Anyways, it is free steam games for ATI and nVidia owners, so everyone but intel IGP owners are in...
Also, once you get it is it is associated with your account... back in the day i used old AGP AMD 9800Pro to associate the games, and then played them on my newer nvidia 7900GS