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