spontaneous blue screen/restart/failure cycle

Sometimes my Windows Vista (home premium) computer suddenly gives me the blue

screen and tells me that it is "dumping physical memory" (as well as to run

diagnostics). Then, it neither goes back to the normal mode nor restarts. So

I am forced to manually shut down the computer (by pushing the power button

for five seconds). Of course, I cannot run the diagnostics that the blue

screen has described because I cannot get the computer back to normal

(non-bluescreen) mode.

But when I manually restart the computer, it does one of the following two

things. Either A) it freezes, thus forcing me to manually restart, or B) it

starts working fine and then gives me the blue screen ten seconds into

operation.

When either of these things happen, I am of course forced to re-start the

computer manually, and thus repeat this cycle.

Fortunately, there is the Safe Mode (which I am currently using so as to

have Internet access). Obviously, permanently using the computer in Safe Mode

destroys the purpose of the operating system's bells and whistles.

Sometimes, the blue screen is followed by the computer spontaneously

restarting, then telling me that it was improperly shut down (and offering to

put me in safe mode).

So, can someone please help me get out of this nasty cycle?