Any chance that you added any new hardware to that machine recently?

Yeah: A 1GB DDR RAM

But it was working perfectly until now. And I bought that at around a week ago. I also bought myself a GeForce 7800 AGP at around a month or two ago.

Could very well be a RAM problem.

Remove that RAM.

Remove that second hard drive as well.

Then you will need a working CD drive.

Boot your XP Home CD into the Recovery Console and try the commands FIXBOOT or FIXMBR

If that does not work the run a Repair Install of XP.

I took apart my xbox and am currently using that as my CD Drive. But the problem is, I have no pad, and it keeps rebooting.

What do you mean by "no pad"?

no controller to keep it active

I'd suggest getting a new DVD/CD drive.

You can find them for @ $20.