My rig has been experiencing episodes of BSODs and sudden blackouts for sometime already (a year or so), but the occurrences have been much more frequent when I started playing TESV Skyrim. I'm not exactly sure where the problem lies, hardware software, the OS, the game, or the game itself; that's why I'm posting this under the Win7 category.
I regularly (once every 2 weeks) clean deleted files and my regs using CCleaner, and defrag the system just as frequently. I also tidy up the rig itself every month.
You should do it with a process of elimination.
-Run memtest overnight, see if that is the culrpit.
-Then comes the cpu, run prime95 on small ffts and monitor your temps. If your computer crashes there it means i) Temps looked ok: if you have an OC, it is unstable. ii) Temps spiked off charts: your cooling is inadequate. Re-seat cpu, Re-apply thermal paste, try again.
-GPU related. Run OCCT video straining test while monitoring GPU temps. If you get like 100C before comp crashes then you need to re-apply paste to your gpu or change cooling solution.
-PSU/Mobo. Even though i would bet right off the batt your problem is PSU related you HAVE to eliminate all other options to determine this.
19 times out of 20 it is the PSU and not the mobo. i) your psu is giving you very little power. No name brands usually supply 60% of named value. GeForce cards usually demand a lot and an OEM psu is poor at providing. ii) your psu is all together bad and your mobo shuts down because of fluctuations on 5v rail.
To determine if it is the mobo you have to try connecting it to a known to work psu. If problems continue, you need to replace mobo.
Thanks for the advice, fellas, but I wasn't able to do tests since I came down with the flu. Anyway, I've decided to stop putting up with my rig and build a new one. I'll keep your advices when I have the same troubles with my future rig. Cheers!