My Laptop is not showing Desktop nor Task manager by C+A+D and C+S+Esc.
not in safe mode, not with command prompt, and also not going to last known good configuration, and can't do system restore point also.

on restarting the laptop welcome screen is appear on clinking user it shows msg
Loading your personal setting..
and within fraction of second shows Logging off..

and welcome screen appear
nothing goes..

should i format my window....

Either a virus or a corrupted windows installation. You can boot from a live cd and try to remove any infections. If that fails, you will need to re-install.

Thanks. i re installed window.