My Computer - Without Any Warning And Without Any Regular Timing - Just Reboots! Is There A Solution To This?

You didn't give any details about your system. I'll assume you're using XP on an average system.
Could be many things. Overheating (too much dust build up or hardware error) other hardware error, bad memory or video chip, power supply failing.

Could also be a bad driver or system update, or spyware installed.
Do a system restore to an earlier point when it was working. Then do a virus and spyware scan.

Your are right...sorry...I did not give too many details about my pc setup.
the reason being I am sooooooooooooo frustrated. This is the pc I use in the office...and it NEVER gave me any trouble...I did not add anything nor installed anything new (as far as I can remember!).

I am using XP pro on a PIII

You can start by downloading the ultimate Boot CD and run some diagnostics, particularly memory tests.
Ultimate Boot CD - Overview