First, test your RAM:
2. BIOS must be set to boot from the DVD or USB before your Hard Drive (drive order)
3. Run the FULL test for at least two hours (or until an error)
If you get errors, test one stick at a time (see motherboard manual for single RAM placement). If one stick tests bad, and one stick tests good then run Windows with one stick to see if you get the BSOD.
In general, you need to:
1) backup e-mail, data, etc
2) *Reinstall Windows, drivers and updates
*Reinstall Windows on a hard drive that has been tested with its diagnostics software. If you use the current drive it will wipe out the data. I still recommend using a different hard drive if possible.
If you still get BSOD after the new Windows install, then it's likely a hardware issue at which point you'll need to troubleshoot by swapping components. It's RARE, but occasionally your RAM can cause issues even if Memtest does not show them. You can confirm by lowering the RAM speed in BIOS (just choose the lowest speed).
Most common causes of BSOD:
1. Bad Memory.
2. corrupted software
3. bad hard drive
4. bad Power Supply
5. bad Motherboard
*You should try using a LIVE CD of Ubuntu and open/close applications in it for a while. It's not conclusive, but if it doesn't crash it could mean either your BSOD in Windows is the HARD DRIVE or corrupted SOFTWARE (either way, I'd reinstall Windows on a different hard drive, then run full diagnostics on that hard drive later).
If it DOES crash, then your BSOD is likely a failed piece of Hardware from my list.