which new games should i get for my PC ?

i already got Crysis warhead for my new PC and maybe i will get spore later.

i think i made a monster machine see the spec:

intel i7 920 processor

Asus P6T Deluxe motherboard

1TB Western digital HDD

OCZ 4gb 1600mhz DDR3

XFX geforce 260 vga card ( i will get another one later for SLI )

Corsair 700w power supply

thanks to squilliam advices 

Left 4 Dead, definitely.

hmm i already got it for my 360 .... u dont know any good exclusive games for pc should i get ?

what genres do you like and get Crysis so you get the full story...

orange box

that will keep you going for quite some time

the witcher if u like rpgs

 I agree. For 29.99 dollars it is practically a steal, and even more as you live in U.A.E (at least your profile says so), where I assume games are even more expensive than in most of Europe.

You get HL2, HL2 episode 1&2, Portal and TF2. Even without TF2 (which I feel is the best online game on PC, and could last you over 100 hours easily), you get almost 50 hours of single player games, all top notch. If you don't own it - buy it.

Definitely get Command & Conquer: Red Alert 3. Dare I say it? Yeah... it's as good as the old ones! =P

Fallout 3 is also a must, best version out there.

The Witcher, King's Bounty, Stalker. Also Counter Strike Source and Day of Defeat source are worth checking if you like online fps and both are very cheap.

Also remember that in most cases PC version will be superior and cheaper to console release.

Don't buy any EA releases on pc they have retarded DRM system which will screw you when you try to resell those games or change your hardware/reinstall OS often.

Galactic Civilizations II, Civilization IV, Company of Heroes, Far Cry 2, Call of Duty: World at War and World of Goo :P