If so, in your tools tab of the steam app, is there a "Stalker ownership check" entry? Any idea what thats about?

I have that there, too. Must be some form of sneaky, sneaky DRM.

I actually noticed this not one week ago. I was going to post about it, too. I have no idea what it is, or what purpose it could fulfill seeing it's the Steam version.
Maybe one of us (not me) will have to brave the depths of the Steam forums to ask there.

I saw that, I couldn't delete the files, which is really odd. Hmm.

no idea why I even opened the tab but this was there, I'm fairly sure I'd have noticed it the last time I wondered what the hell the tools tab was for

First time I used that tab, it was to download TorchED. Then I didn't even bother using it.

LOL @ the paranoia over at the Steam-forums.
Michael: there doesn't appear to be any files to delete, it's just a menu item basically.

Aren't all three games through different publishers? That might make such promotional offers very difficult. Although that might have been their original intent.

Well it claims to be using 41Mb and being 100% ready so I'm wondering what the name of fuck that can be. 41MB to verify ownership of a game??

Quote some guy on the Steam-forum:
There is no executable file for it and the only data files I have found associated with it is. Steam\appcache\app_41710.vdf. Also I bet that the 41 megabytes listed in steam is simply counting the winui.gcf which is actually 41 megabytes.
In other words, STALKER ownership check is not data or executable code, so it doesn't run in memory, nor it a file for a file scanner to scan. How exactly do you scan the program when it is only a bit of data telling steam to show it in your tools bar of steam?

It contains a text file of the accounts of everybody who purchased Stalker on Steam. It then checks whether your account is in the text file every time Steam starts to ensure the validity of your purchase. After all, you -could- be a guy with root access to the Steam servers who had illegally added STALKER to his account, or you -could- be a friend or relative of said person.

Yeah upon reading the thread, I'm guessing its something that was accidently triggered and showed up in the tools tab. One of these days valve might get around to removing it and then the forums will explode with conspiracy theories about them trying to hide things

Or maybe it's just a way to activate Call of Pripyat retail on Steam.