To restore the registry
Open Registry Editor
Click Options, and then click Print to print these instructions. (If you are using the Help and Support Center, click Print above the topic area.) They will not be available after you shut down your computer in step 2.
Click Start, and then click Shut Down.
In the list, click Restart, and then click OK.
When you see the message Please select the operating system to start, press F8.
Use the arrow keys to highlight Last Known Good Configuration, and then press ENTER.
NUM LOCK must be off before the arrow keys on the numeric keypad will function.
Use the arrow keys to highlight an operating system, and then press ENTER.
Incorrectly editing the registry may severely damage your system. Before making changes to the registry, you should back up any valued data on your computer.
To open Registry Editor, click Start, click Run, type regedit, and then click OK.
Choosing Last Known Good Configuration provides a way to recover from problems such as a newly added driver that may be incorrect for your hardware. It does not solve problems caused by corrupted or missing drivers or files.
When you choose Last Known Good Configuration, Windows restores information in registry key HKLM\System\CurrentControlSet only. Any changes you have made in other registry keys remain.