Check your power supply for voltage drop.
Update your graphic card driver.
Hard Drive bad sector can make system blue screen, Use Hard drive tool from manufacture to test your HD for bad sectoralso some free tool can test and repair bad sector search on google.
Bad memory can cause blue screen, Use memtest86 boot it from CD or USB let it run until 2 passed without any error.
Thanks for the replies! Am I likely looking at a power issue then? I think hard disks are OK because I was still getting the blue screen after I unplugged them both. Windows is on an SSD, which I don't think can get bad sectors?
PSU is Corsair TX850 so should be quality, though I have just had a high wattage graphics card die on me and got the system running again by replacing it with a card using half the power. Maybe the other card didn't actually die then and PSU is just failing to provide power?
This isn't a new build by the way, April 2010 and has been running happily until now. A system restore has got Windows booting happily again, could be possibly be a Flash update I just installed? If the PSU is dying, would it be worth buying one of those PSU testers? Would that give specific details of the fault (if there is one)?
A PSU tester is a waste of money, they only give a go no go indication. They would not detect a dying PSU. Substitution of the supply is the only test that a home user can perform. The chances are your problem was a software one, but it would be a good idea to run memtest86 for at least three passes.
Appreciate the advice - I know blue screen crashes are not the most interesting topic of conversation :-) I'll test the memory to be sure and then just hope for the best I suppose. I can't return the PSU if I'm not certain it's faulty, and it's not a cheap unit to replace just in case it's faulty. Googling blue screens after Flash updates threw up quite a lot of stuff, though they date back throughout this year and last year too. If memory is OK though I think I'll just have to put it down to that update.