how do i get my OS to load??

my computer (emachines T6536) has been runing a little slower than normal lately and it has been locking up and i have to hard power it. i have never had a problem after hard powering it before but now when i turn it on it asks me to boot into safe mode, the last known good setting, or just start windows normally. whichever choice i pick it starts to load windows xp and after about a second of loading a blue screen flashes but so fast i cant read any of it and it completely restarts on its own. i have tried using the system restore disc and it starts to load that as well and then freezes as it is loading so i cant even do a system restore. i can however go into my BIOS settings and boot menu but i dont know enough about them to make any changes. can anybody tell me what could possibly be wrong and what to do to fix it?