BSOD using Google Chrome, COD MW3, Steam. Invalid crashdmp.sys

Hi,
last days I have series of strange preoblems connected with my computer. I have Win7 Home Premium OEM on new computer (bought about a month ago). System is already activated, but I haven't called Microsoft support yet. I have 500GB disc: half is 250GB partition for system, and half is not in use.

Problems started when playing COD MW3 (game is on Steam platform). I got "File corrupted" error on game startup. I found an option of checking integrality of files on Steam - it found problem with some (I think it was seven files, I'm not sure) and started downloading those from Steam servers. It was rather big package, about 1,5GB.

Everything was right, but in two days there was another problem: COD said it couldn't load an image. Well, I made integrality check one more time and Steam had to download some files again (this time somethink about 500MB, so it was sth different probably). I had this problem one more time (package size was different), everything was OK for two days.

It can be important: I don't know how Steam update works, but it installs downloaded files automatically.

Yesterday I got BSOD after a COD match in the moment when it usually goes to the wait room after a game (I suppose that game tries to write something on disc or send to Steam servers then). I only noticed that was MEMORY_MANAGEMENT error. It's strange because of good hardware configuration.

Since then i have had many more (while using COD, Steam or Chrome usually), there was always problem with memory, don't remember errors literally. Sometimes system restarts while loading data (there is an animation of the logo, it crashes in half) and after restart "System fix on startup tool" opens (free translation, I'm Polish ). There is a problem, in log it says about "Checking system files integrality" failure (errorcode 0x2).

I made sfc /scannow - it found problem, but can't resolve it automatically. In log (attached) there is an information that crashdmp.sys is invalid, checksum doesn't match. I scanned system32/drivers folder with free Avast, everything OK.

I also tried updating using system disc. It reports failure - errorcode: 0x80070241.

Sometimes system works, I'm writing this post and everything is OK so far.

I have no idea what to do. So far I only made a copy of the most important files. Can anybody help me?

Refresh. Can anybody give any hint?

Ref. No help?

I uninstalled CoD, but it doesn't help.

F5.