Try running in safe mode to see if it works ok.
Then maybe click on last good configuration or system repair.
or maybe try this.
- Turn off computer ,then turn on and start tapping F8
- When the Advanced startup options appear Select Safe mode With Networking
- Open internet explorer goto google.com ,download Hitman pro "32-bit or 64-bit depending on your Os"
- Run Hitman pro ,let this scan the computer
- Activate Free Licence
- Reboot Pc