Sounds like a rootkit virus.
Can you start in safemode?
If so you may want to go into safemode with networking enabled.
Download Malwarebytes(it's free) and update it then run a full scan.
Remove everything it finds.
If that doesn't solve your problems rkill which is also free might kill the virus.
One other thing to try first, from safe mode do a disk check of your hard drive. If you can’t get into safe mode then boot from the Windows CD and chose repair this computer and let it automatically try and fix any problems.