Hello katvall
The problem doesn't seem to be hardware related. This has something to do with the Windows.
The easiest and straightforward method to resolve this issue is to restore your Windows back to an earlier restore point. However since you are unable to do anything after logging on, you may want to try booting your Windows in Safe Mode and then restoring the OS to its earlier restore point, i.e. the date when you believe the computer worked fine.
If you have Windows 7, you can power on the computer and keep pressing the
F8 key repeatedly until you see the
Advanced Boot Options menu. From there, you can go to the Safe Mode and then
restore the system to the desired restore point.
On the other hand, in case you have Windows 8 installed on your computer, you can follow the step-by-step instructions along with a video tutorial
given here to start the operating system in Safe Mode.
Note: Even though the given tutorial is for Windows 10, the process to get the job done in Windows 8 is identical.
Once in Safe Mode, you can follow the steps
given here to restore Windows 8 to an earlier restore point. (Expand the
Restore your PC to an earlier point in time link on the redirected webpage to get the detailed instructions.)
Let me know which of the above solutions worked for you. Good Luck!!