I have encountered BSOD mostly when I had added an incompatible hardware of faulty drivers.
I had internal TV tuner card initially, then one day when I installed a graphics card too, suddenly I started feeling the aftereffects of conflict between these two cards. I had to remove tv tuner card after which the system became stable...
that graphics card again started giving problems when it became loose (loosely connected on the slot). BSOD surfaced again...
Conclusion is it is mostly because of hardware issues only. In your case, perhaps you had bad drivers for any hardware which got corrected after the re-install.