you ALWAYS see the blue screen. even if for only a split second. if you aren't seeing a blue screen and you turned the reboot option off its not happening.
So. when does it restart? what are you doing? what are your system specs? didnt really give us any info.
could be a possible hardware problem or likely overheating which will just cause a crash. have you run memtest86+? have you checked your CPU/gpu temps? theres really no reason to use the blue screen, windows gives the error in a popup when you reboot if there was one. have you at least checked the event log?http://windows.microsoft.com/en-us/windows7/What-information-appears-in-event-logs-Event-Viewer