Most likely to be a video card/driver problem. CS6 puts a lot more demand on them than previous versions. And having a sysem 4 years old probably means it is not up to the task. You need at least 512 kb of VRAM on the video card and an updated driver (from GPU makers site).
What OS and how much RAM?
It is difficult to usually impossible, to recover a corrupted psd. I would strongly urge you to save under different name and save frequently.
While not directly addressing the PSD issue, a BSOD is serious, and is often caused by a couple of factors:
OS issues with drivers
This article might be helpful in tracking down the cause: http://forums.adobe.com/message/3465303#3465303
I would fix the BSOD as soon as possible.
My OS is a windows vista and I have 4 GB RAM. Currently I'm saving my psd's under different name and saving frequently. Besides the occasional BSoD photoshop works pretty well on my computer. No lags, freezes, or anything.
I've tried a bunch of stuff to fix my BSoD problem but I'm not sure any of it has helped. Perhaps only a decrease in frequency. But I will take a look at that article. Thanks.
Suggest you condider getting a new computer before you waste a lot more hours on these BSODs. You need to be able to rely on it. System crashes are not normal occurrences.