If you have got an NVIDIA card then head on over to steams site where Valve is offering for a limited time Portal: First Slice which is an extended demo of the full game.

You can also can also download Peggle Extreme, Half-Life 2 Deathmatch, and the Half-Life 2 tech demonstration level The Lost Coast free of charge from that same offer.

All you need is an NVIDIA card and the latest version of Steam on your computer and your ready to go.

The offer can be found >> HERE <<