BSOD at random times

Alright, so my computer is functioning properly without anymore BSODs, but it has froze twice. this isn't a frozen where you can just Ctr+alt+del it. When it freezes the mouse and keyboard stop working. the status lights on the keyboard are still on (the Numlock is still glowing) but when i hit the numlock key the light doesn't change... I don't know what my problem is, but it may be my RAM? also just for good measure i would like to clean the contacts on my RAM. do you use rubbing alcohol? that is what i have been told.

Thanks,
Brennan