Well I'm having this problem and it annoys the crap outta me.

I bought STALKER Shadow of Chernobyl last Friday, installed it and played it, it rocks, it's great, blah blah blah all the usual stuff.

2 days later I installed a mod, but it changed things that I didn't want it to change, so I deleted the "gamedata" folder it created. Then the game refused to load any saved game, I couldn't create a new game either, because when it was loading, a pop-up showed up saying that the X-Ray engine detected a crash and such.

I reinstalled the game, but it didn't work. So I uninstalled the game, cleaned the registry, deleted the saved games, installed the game again and applied the 1.003 patch.
Then I tried to play. It worked correctly until it froze. I thaught it was because my comp had been on for like 8 hours, so I shutted it off.

The next day I started the comp and tried to play, but it was pretty much unplayable. It froze 4 times of 4 times I tried to play.

My basic system specs are:

Processor: Intel Pentium 4 3.2 GHz
RAM: 1GB
Graphics card: ATI Radeon X1300 PRO

I don't quite get what's wrong. I have to run STALKER at 800x600 with all the graphics at low and it 's still laggy, though I don't care about the lag, but what the hell can I care about if I can't even PLAY the game? This pisses me off, seriously.

And if I didn't say it clearly, the game didn't freeze before I applied the patch.

I didn't feel like reading all of that so just try to reinstall all of it.

If that doesn't work don't be an idiot and delete the gamedata folder....that's just plain stupidity.

Plain stupidity is posting without reading my message.

I said I reinstalled all of it, and the gamedata folder was created by the mod, all the important files of the game are in the "bin" folder.

I have a pwnx0me comp and it lags for me too
And it does the freezes aswell, but thats rare...
I played the pirated, getting my official copy back in a few days, then ill be able to install the FECKIN' AWEASOME MOD THAT ALLOWS YOU TO DRIVE NOT COMPLETELY BUSTED VEHICLES, BE ABLE TO BUY ANYTHING FOR ANY MERCHANTE, BE ABLE TO CARRY 300KG!!!! NEW TEXTURES AND BETTER WEAPON DAMAGE!!! W00T!!!!

It might freeze on your comp cause you dont have nuff' RAM... Might be that...

I know about people playing with about 500 megs of RAM and not getting absolutely any freezing, so RAM is discarded as the problem...

Hmm... games can be funny like that. There will be 1 or 2 small but key files or registry entries stop the game from running properly.

I know you said you cleared your registry, but are you completely sure you got it all?

Could it be a bug with the patch?

Edit: Never mind, I just noticed you said it didn't freeze before you got the patch.

Have you noticed anything happen just before it freezes, or does it just do it randomly?

First off, for freezing. Get speedfan, google it, and try running the game with your comp fans set to full. STALKER isn't the best at resource management, so you may need to close down a lot of other applications for it to work. Thirdly, STALKER sucks at loading sounds from the files, at least for me, if anything else is accessing the hard drive, so just close down pretty much everything you're not using, and see if that works.

Interesting.
I checked the options and saw that the illumination levels were at the lowest (the one that uses DirectX 8.1 technology). I changed it to the medium level, started the game, and played for 25 minutes without freezing (a bit of stutter sometimes, but I guess I'll have to live with it).

That was yesterday, I'll try to play more today and see what happens.

And, well, thanks to everyone for the suggestions and stuff

Hmm... that IS odd.

But it could be a possible cause. My friend had a pretty high end computer, but when had the ingame music of Morrowind turned all the way down, the game would lag like crazy.

Definitely it IS the cause.
Yesterday I played all the way from passing through the mercenary camp in Cordon to the underground level, wich lags like hell by the way, with no freezing.