Not an expert or anything, but one of the simple things you could try is the following:
1. Boot to BIOS
2. Select Safe Mode boot
3. Let the PC boot to Windows and sit for a while - if that works, you can already call it a success
4. At this stage, windows should detect/fix any common problems
5. Restart and boot regularly
Again... not a fool proof solution, but it might help :)
If that doesn't help, you'll still want to do steps 1-3 and see if it's stable in Safe Mode. From there, you can scan the PC with an antivirus/malware program or try the windows troubleshooter.
If it's not stable in Safe Mode and for some weird reason you had a back up of your system... use the built-in system recovery from Windows to an older timestamp.
Good luck, hope someone will be able to provide you more accurate help :)