Hi, thanks for the responses.
I updated the driver as per your responses and it is now showing a 2009 date. The crashing persists, however - the only real change being that the screen now goes black instead of white or brown before restarting.
I tried downloading cpu-z and gpu-z but it seems I can't install in Safe Mode. I'll have a couple more tries at getting them to run in Normal mode before it crashes.
I would be surprised if it was a GPU heating issue because I always used a program called Afterburner to monitor the temperature and never had anything above 75; besides, it crashes soon after startup without doing anything remotely GPU-intensive. I also cleaned all around the fans but to no discernible effect.
EDIT: Have now been successfully running for about 15 mins. GPU temperatures are hovering around 50 degrees; not exactly sure what I should be looking for in CPU-Z, though. Have three messages in Windows Action Centre:
Address a problem with NVidia Graphics Driver - NVidia Graphics Driver has stopped working 2 times.
Install your power management system driver. (just finished doing this).
Download an update for USB 3.0 Host Controller driver.
I'm about to reinstall the NVidia drivers again, just in case, but this will be the third time since I did the clean install of Windows.