e mirrors here. If you do already have it on a CD, skip to step 3.

To run it, create an ISO and burn it to CD you can read the instructions here. I wont write the instructions here because the ones on the previous link are better and this article is more targeted at computer technicians and most of them already have this CD.

2. Once the CD has been created, goto the BIOS and make sure your CDRom is set as the first boot device. Start up the computer with UBCD4Win in the CDRom and you will have some boot options. Choose the “Launch The Ultimate Boot CD for Windows” option.

It will take a few minutes to load fully, but when it does you should see a Windows XP like interface like in the picture below:

3. In the UBCD4Win interface, goto Start > Programs > Registry Tools > Registry Restore Wizard.

4.The program will then ask you which Windows registry you want to repair. In most cases, it’ll be C:\Windows. Choose the copy of Windows you want to repair and press Next.
Repairing Windows Hive: Select Windows Install

5. Choose “Fix the system registry to that of a previous state” and Press Next.
Repairing the Windows Registry Hive

6. You should now see a list registry restore points. Choose one with a date a few days before the issue first occured.
Repairing Windows Registry Hive

7. Wait a few seconds for it to restore the registry. Press Finish and restart the computer. The issue should now be fixed. If not, it may be a sign of a greater issue like hard drive damage.