Hi,
It may be worth trying windows System Restore as follows.
Shut down the notebook. Windows System Restore is usually best run in Safe Mode. Tap away at f8 as you start the notebook to enter Windows Recovery Console. Use the arrow keys to select Safe Mode and hit enter. When this has loaded, from the Start Menu, click All Programs, click Accessories, click System Tools and launch System Restore. Pick a restore point at least 24 hours before the validation issue occurred and then proceed with the restore process. When complete, Windows will reboot as normal.
Regards,
DP-K