YouTube - HL2DM - Free Online Shooter
if you read the description in that vid you'll see 2 links (both are legit) about getting a few great games for free taht would normally cost you like $20 lol.
BUT you must install a program called steam which is basically a PC community equivalent of PSN or XBOX live, but only free like PSN (I'd say better service too but it depends on your internet >.>)