This doesn't have anything to do with GOG but since you guys are experts in the field of DRM I thought I'd come to you with this before anyone else.
I have purchased STALKER (Es tee ay el kay ee ar) Clear Sky over Steam. I have only installed it 3-4 times so far. Starting with install number 3 or 4 whenever I try to boot up the game on my laptop, I see something TAGES related then a big blue screen of death. This does not happen on my other computers with STALKER installed. I have some things installed like Daemon Tools that you would think TAGES might get upset about, but I assure you that STALKER was running just fine before.
I think it might have started right after Steam updated the game. Since then I have tried
-uninstalling and reinstalling the game
-uninstalling Daemon Tools
-uninstalling and reinstalling Steam
-disabling my internet connection when starting the game
-updating all of my drivers/BIOS
-starting the game in different compatibility modes
-installling a pirated copy of the game with a crack
None of this has changed anything. I'm afraid TAGES might have caused some permanent damage to my system after that update that prevents me from playing the game at all.
Any ideas guys?

try :-
-uninstall stalker clear sky from steam (delete content i believe its called)
-download and run the tages removal tool
http://www.tagesprotection.com/main.htm?page=minimum.htm
-re-download stalker clear sky from steam

I've done all of that.

try running the .exe directly from its directory and run as administrator.....never know it might help....

Nope.

just a small note that uninstalling daemon tools doesnt fully remove it.
still some registry entries remain afterwards. possibly with tages aswell.
you could try running ccleaner after unisntalling them both, or something more effecient at registry cleaning like winaso.
but the clear sky forums surely will get more results. this isnt a DRM-knowledge bank. the DRM-Free logo on this website is simply there to pander to the whiners that dont like drm.

They may be 'whining' because they've had an experience similar to this one. I certainly would be.