first run checkdisk:
if you do not have Recovery Console installed, then run from the start menu
go to start, run, type in cmd
in cmd type in chkdsk c: /r and press enter
type Y for yes and press enter
type exit and press enter
restart pc, allow checkdisk to finish and run again
you can see report in event viewer/applications/winlogon
report back after running checkdisk until there are no more errors found and we can troubleshoot further.