Gshields

PROBLEM My computer won't boot. A blue screen appears to say an error has been detected and that I should run a virus check etc. It won't boot in safe mode either. I can't get it to boot in any mode whatsoever so can't run any anti-virus programs. HISTORY My virus software subscription ran out and the computer was used for 2 months without any anti-virus software. I subscribed to my anti-virus software for another year and tried to undate my virus definitions. However there was an error with this and it wouldn't work. A couple of days later it would start and I got the blue screen as described above. I do not have a boot disk and have no idea what to do next. Any help would be much appreciated.