ComputerBB

hi, new to computer building and fixing so go ez on me. a few days ago my PC started rebooting when playing a game. I called windows help line and the person walked me in trying to fix it. long story short be the end of the call my pc would only boot back up to the welcome screen then reboot over and over. she told me my harddrive had went bad and needed a new one. the next day I go buy an 80g maxter and put it in the pc. now I cant even get it to power on. when I hit the power I get nothing like its dead. as far as my PC stats im doing this from work. p4 1.6, windows xp home, over 1000mb mem, Ti4800 gfx, maxter 80g HD, forget the mainboard its a msi(?), 4 or 8x agp or something like that. if you can help me plz let me know