The Windows registry is a critical data storage center for every version of the Windows operating system. It is where commands are stored for virtually every system function, so when one or more of these registry keys is deleted, it usually limits system performance or functionality in one way or another. If you've either intentionally or accidentally deleted an important registry key that you need to restore, choose the recovery method that best fits your situation.
If the Computer Boots Up Normally
Start Windows and wait for it to fully load.
Click the "Start" button. Look under the "Accessories" sub-folder and then under the "System Tools" sub-folder. Click the "System Restore" icon.
Select "Restore my computer to an earlier time" and click the "Next" button.
Choose a date on the calendar from before the key was deleted. Click this date, then click the "Next" button.
Wait as the computer restores to this point. When the restoration is complete, the deleted registry items will be restored.
If the Computer Does Not Boot Normally
Reboot the computer. As soon as it begins booting up, start tapping the F8 key repeatedly.
Wait for the boot menu to appear. When this menu appears, use the arrow keys to scroll down to the "Safe Mode" option, then press "Enter" and wait for Windows to boot into safe mode.
Complete Steps 2 through 5 in the above section to restore your system to a period before the registry keys were deleted.
If the Comptuer Does Not Boot in Safe Mode
Reboot the computer. Start tapping F8 again as soon as it begins booting up. Unfortunately, if your computer will not boot even into safe mode, it is an indication that critical registry keys have been deleted and the operating system will need to be reinstalled.
Open the CD-ROM drive door when you reach the boot menu. Insert your Windows installation disc and close the door.
Select the option from the boot menu that will allow you to boot directly from the CD-ROM drive. The exact wording of this command varies depending on your BIOS and/or version of Windows, but it will typically be "CD-ROM" or the letter designation of your computer's CD-ROM drive. Press "Enter" when you've chosen the right option.
Wait as the system reboots. It should boot directly to the Windows installation wizard.
Follow the on-screen prompts to reinstall Windows and restore your system keys.
Things You'll Need
PC with Windows
Windows installation discs
Never alter registry keys unless you know exactly what you're doing.
Reinstalling Windows, while it may be a necessary step after deletion of certain registry keys, may also delete all your stored data depending on your system options. If you must attempt to recover this data, take your computer to a repair specialist to have your options assessed. Data recovery may not be possible.