Computer keeps crashing non-stop.

What do you mean by crashing? Powering off? Shutting down? Blue Screen?

on windows 7 it had 4 different types of blue screen. on XP its just freezing completely. it will never freeze for a few seconds, when it freezes then thats it, needs to be reset. the mouse seems to respond with it flashing but everything on the screen is just frozen.

A good first step would be to get memtest to see if it's your RAM that's bad.
http://www.memtest.org/

i started getting errors after the 5th pass. does that mean i need new RAM  

you have (2x2GB) meaning two memory dimms.

When you get memory errors pull one of the dimms and retest. If it passes, take the good one out and put the other one back in. If it fails return it for exchange. if they both work fine as the only memory dimm then try them both together again. Sometimes re-seating the memory fixes the problem.

Good call fun500 on the memory test.

p.s. you are hoping that the memory was bad given that the memory test failed. The other options are bad bios setting for voltage/speed (force them manually, do not let the MB bios detect your memory speed especially with low voltage or high performance memory) or something else bad that is seen as a memory test error (MB, bad card in pci slot, etc.) Memory is about the cheapest problem you can have.