I run Windows XP, my computer will not boot up in normal or safe modes and goes to a "no signal" stage then back to start.

Try booting to your XP CD and using the Repair option.

Would try above mentioned repair

If getting "no signal" on the screen, usually would indicate something with the monitor or video card

See if you can get hold of another monitor to see if that will help, if another monitor still gets 'no signal' might be looking at a possible bad video card

I had this same thing happen to a computer I was working on.
It turned out to be that the video card resolution was set too high for the monitor to handle.

So every time the computer would boot, it would show windows loading then it would go into "no signal" and restart.

FIX: when it restarts hit F8... then select "enable VGA mode" this should boot you into windows.

Let me know if it works.
Thanks,
latingmex