Take a look in c:\windows\minidump and see if there are any .dmp files dated this past weekend. If so, please upload them. Also, you can look in Event Viewer, but candidly it will probably be tough to identify what we need from there. Next time(s) the blue screen pops up just make note of the specific error message / code. If the codes are different each time then you have a piece of hardware that has failed or is failing. It could be the PSU as patio suggested or it could be the motherboard, cpu, or something else.