Not rebooting.after suppotassist update

Help. Last night was updating the supportassist tool. It said new version available and started download. After about 20min it stopped downloading and everything froze. Left it on over night and still frozen.so turned off and when turned back on will not boot.get dell page and circle goes round for few seconds then stops. Done f22 and diagnostic seems to be no errors. Support assist and os recovery from f12.just gives blue screen that turns black and seems to turn off.tried all trouble shooting options. Supportassit will not launch os recovery tool and Microsoft will neither reset PC and says no system image can be found. There seems to no longer be any system restore points.sfc says corrupt files repaired but not rebooting .have I lost my os. Was using laptop all day seemed to be OK.