hmmm....
when you login, do you normally have to put password in or does it log you direct to desktop?
If you have to put password in, don't. Instead, look at the 3 icons in bottom right of screen, one is power
open the power menu so it shows sleep, shutdown and restart
while holding down the shift key, click restart
PC should restart and load advanced start up
choose troubleshoot
choose advanced
choose start up options
click the restart button on screen
choose a safe mode (it doesn't matter which) by using number associated with it.
PC will restart and load safe mode
is PC slow here? if its normal then the problem might be a driver on your PC. right click start button and choose device manager and see if any unknown devices or warnings
sometimes just booting into safe mode and exiting again can fix errors
another choice is restart PC again, come back into advanced startup like I showed above and run start up repair
choose troubleshoot
choose advanced
choose start up repair - this will scan PC and maybe fix this - will ask for logon info
If your PC auto logs into desktop, getting to this menu relies on ctrl alt del again and choosing log out as it will bring you to the login screen mentioned above. You may need to restart PC to get ctrl alt del working again.
is there anything on C drive you want to rescue? try making this on another PC: http://www.howtogeek.com/howto/windows-vista/use-ubuntu-live-cd-to-backup-files-from-your-dead-windows-computer/ << as this will let you copy files without windows acting dumb and stopping you. You might be best doing a fresh install so back up everything you don't want to lose.
Also, on another PC, download the
Windows 10 media creation tool and use it to make a win 10 installer on USB
change boot order in BIOS so USB is first, hdd second
boot from installer
follow this guide:
http://www.tenforums.com/tutorials/1950-windows-10-clean-install.html
when you reach screen asking for licence, click "I don't have a key" and win 10 will continue to install and reactivate once finished
On the screen where you choose where to install win 10, if it gives you an error about GPT drives, delete all the partitions on the hdd and press next. If it still gives error, cancel out of the installer and restart PC and start installer again, it will accept next on that screen this time (some PC just need a restart here)