Start up issue, blinks at the top left corner on start up.

My Lenovo Thinkpad T440s laptop ( windows 10), couldn't boot up to windows, during start up, Lenovo logo appears then it goes to a dark screen with one dash blinking at the top left corner. I tried the diagnostic tests (all passed) and boot option but couldn't solve the issue.

I have already saved my data by removing the hard disk and connecting it to another computer but i want to fix the issue with out formatting the laptop.

For some reason i couldn't run safe mode start up as F8 is not working.

Any solution is much appreciated.

Regards

Tesfa