If you can go to microsoft, download memtest.exe. it's a memory tester. If you can't find it on microsoft then just google it. Try testing your memory. Restarting on a computer can be caused by just about anything, heat, HD, Memory corrupt, motherboard screwed up somehow etc.... Put memtest on a floppy after downloading it and boot from the floppy, it'll run 6 tests continuously and it will tell you if anything is corrupt. Try doing a checkdisk on the HD. Have you heard any clicking or has the HD gotten louder recently? If so replace it. If not then you might want to look at your powersupply and upgrade. Then put all the fans back in so it can cool properly. After that, if you still ahve problems you might have to take it to get looked at or have one of your friends look at it with you. Somtimes it takes a new perspective to figure things out. Hope this helps.