Have you tried chksdsk /f ?

I have had similar problems and fixed them with SpinRite 6 from Gibson
Research (www.GRC.com)

www.FreeComputerConsultant.com

alnoor.jiwani******.com wrote:
> I get "operating system not found" on warm boot
> i.e. ctl-alt-del / restart.
>
> The system works just fine if started form power-on/off (cold boot).
>
> Cannot understand why this would be the case. The problem
> started after I uninstalled my firewall. I have tried since to
> install/re-install again without any solution.
>
> I have aslo done "fixmbr" and "fixboot" from
> recovery console, but my problem still presists.
>