For those of you interested or curious here are the official specs from the readme file while installing S.T.A.L.K.E.R.
SYSTEM REQUIREMENTS
MINIMUM SYSTEM REQUIREMENTS:
Microsoft® Windows® XP (Service Pack 2) / Microsoft® Windows® 2000 SP4
Processor type : Intel Pentium 4 2.0 Ghz / AMD XP 2200+
512 MB RAM
10 GB available hard drive space
128 MB DirectX® 8.0 compatible card / nVIDIA® GeForce™ 5700 / ATI Radeon® 9600
DirectX® 9.0 compatible sound card
LAN/Internet connection with low latency Cable/DSL speeds for multiplayer
Keyboard, Mouse
RECOMMENDED SYSTEM REQUIREMENTS:
Microsoft® Windows® XP (Service Pack 2) / Microsoft® Windows® 2000 SP4
Processor type : Intel Core 2 Duo E6400 / AMD 64 X2 4200+
1.5 GB RAM
10 GB available hard drive space
256 MB DirectX® 9.0c compatible card / nVIDIA® GeForce™ 7900 / ATI Radeon® X1950
DirectX® 9.0 compatible sound card
LAN/Internet connection with low latency Cable/DSL/T1+ speeds for multiplayer
Keyboard, Mouse
HIGH SYSTEM REQUIREMENTS:
Microsoft® Windows® XP (Service Pack 2) / Microsoft® Windows® 2000 SP4
Processor type : Intel Core2 Duo E6700 / AMD 64 X2 5200+
2 GB RAM
10 GB available hard drive space
512 MB DirectX® 9.0c compatible card / nVIDIA® GeForce™ 8800 / ATI Radeon® X2800
DirectX® 9.0 compatible sound card
LAN/Internet connection with low latency Cable/DSL/T1+ speeds for multiplayer
Keyboard, Mouse
Note: recommended specifications provide optimal experience for single player and up to 4 player/medium size map multiplayer
I think its a nice addition to have the HIGH specs for those who want to max it out.
Those specs are wildly inaccurate. In reality you can play STALKER on the following quite comfortably
LOW:
CPU: 2.5GHz P4 or 2.0GHz Athlon
RAM: 2x512MB, preferably low latency PC3200
Graphics: 128\256MB 9600\9800 Radeon or GF6800NU (FX series really sucked)
MEDIUM:
CPU: 3.2GHz P4 or 2.5GHz Athlon
RAM: 2x512MB PC4000, running @ PC4000, preferably in sync with the FSB
Graphics: 256MB Radeon 9800Pro\XT or GF6800NU
HIGH:
CPU: 3.8GHz P4 or 2.8GHz Athlon
RAM: 2x1GB PC4000 or better
Graphics: X1800 series or GF6800 Ultra or better
For the record, I'm running 2x1GB, 2.85GHz A64 and a X1950Pro @ 621\1.5GHz, ALL eyecandy maxed, 2xAA 16xAF 1280*1024 resolution, smooth as a babys bum. I would run 4xAA, but theres no need on a 17" monitor. I suppose if anyone is interested I could use fraps and compare FPS.