The first thing I think of in a case like this is the memory is faulty. try removing and reseating it. Try booting with one stick only if your computer can run that way. Switch out the stick for a different one if it still hangs.
What exactly do you men when you say the computer froze? Does the mouse pointer move? Does the Numlock light go on and off (you’ll need to repeat that 10 or so times because the keyboard has a buffer). Try booting to Safe Mode with Command Prompt.
Has anything changed recently? New software installed? New hardware? Had you just applied an update from MS?