VAIO FS760/W Blue Screen and other Errors

Hi, I recently acquired a Sony VAIO VGN-FS760/W. It had some known crashing problems and I tried to fix it. My cousin who originally owned it had only upgraded the memory to 1GB pc2-5300. He told me that it crashed frequently. I tried installing Win 7 32 bit and it BSOD'd when I accidentaly enabled Aero. I tried the original VAIO OS recovery (F10) and it had many problems (including random reboots and many different BSODS). I formatted the hard drive when I tried installing XP from the disc. It worked for a while but started giving me the lss. error. I didn't know if it was the sign of a w.32 virus or an error, so I troubleshooted both. I got it to start by pulling the motherboard battery and resetting it. Finally I reached a dead end, with windows xp and the BSOD code c000021a. The previous owner had clumsy tendencies and probably dropped it a lot too. Could the memory be the problem? Any solutions? Thanks.