How come my computer is rebooting before it ever gets to Windows?

I'm running Windows XP Pro, my computer is a pretty dang good PC and I play games on it all the time. I turned it off the other day and now when I start it, it boots up normally until it gets to the point where it asks me to run Safe Mode / Safe Mode with Networking / Safe Mode with Command Prompt / Setting that last worked / Run Normally.... no matter what setting I choose, it will start loading Windows then it starts all over again (it doesn't make the typical reboot sound either it doesn't seem like, but that could just be me)

I tried hitting Delete during one of the screens to load the settings thing, I hit Load Default Settings and saved it and tried them all again, nothing changed.

I'm wondering if a virus could do this? Is there any way to maybe load a back-up or do something to give me a little control over it? I don't know what all the stuff is in the Settings when I hit Delete, but it just lets me really Disable/Enable a lot of things...

I'm using different comp

How come my computer is rebooting before it ever gets to Windows?windows vista home premium

you did not shut down properly that while it runs in safe mode then wheather you have touch the necessary files without knowing, talking about virus , is your system not protected by anti virus life MCAFEE or strong anti virus. check for your seting and install a better anti virus. stop using delete if you not the what is the problem . call a good techincian (computer engineer) to check for u