Also, was it a blue screen, or a popup?
If it was a popup, it might be a virus preventing you from correctly booting your computer.
If it was a blue screen, it might be heat-related (in which case you only need to let it cool down for a bit and pay more attention not to block air vents in the future) or a piece of RAM (or even the HDD) that came loose (in which case you just have to re-seat it - and yes, I've had my HDD come loose a couple of times before).
Worst-case, the GPU (or IGP, or chipset) bit the dust, meaning new laptop needed
Oh, I just remembered: I once had an Asus notebook (F3E-based) that randomly crashed, no apparent reason. Turns out, the Kingston memory module the reseller installed as a freebie, while perfectly OK, was incompatible with that laptop model, and the incompatibility ranged from 100% OK operation to random lockups to 100% inability to power the laptop up. Go figure...