Have you any restore point? what OS are you running? if its win7, not sure about vista, or 10, but it'd be unsurprising if all three such abominations did something similar, you might be able to force it to think its been shut down incorrectly by booting it up and straight up just turning off the power, either through the computer, or directly pulling the plug if the power button triggers a menu and the lock-ups won't let you get past or to it, the kind of thing that would likely trigger safe mode options during the bios coming online during bootup before windows starts.
On this machine (currently the HD in it is running win7 *fingers down throat moment* ) there is another sort of boot choice menu before that comes into play if its been incorrectly shut down by turning it off, you only get IIRC 3 seconds to choose, or it'll boot into the safe mode choices, but there is a menu which allows one to either boot as normal or the lower option, (down key) takes you to a point whereby the backup image, a very basic clone of (unregistered) the OS, can be used and it'll take the thing right back to the start.
Be aware doing so is a commitment, it nukes the thing and reinstalls the OS from scratch, data is not preserved. Once you do it, it'll wipe the drive irrevocably of EVERYTHING. And reinstall the OS from what appears to be a hidden partition. Might not help if you've gotten a boot sector virus, not sure, but I had to use it once after some malware slipped through the scanners, got detected but AV, etc. was unable to kill it and make it stay dead. Thing was some kind of freak virus-zombie that kept on moaning for brains even after having its head shot off.