Follow these steps to backup your registry key.

1] Start your computer normally.

2] Click on start and then click on RUN, in run box type
%SystemRoot%\system32\restore\rstrui.exe, then click OK button.

3] You can see one page appear on the monitor screen. On the Welcome to System Restore Page, click on creates a restore point and then clicks NEXT.

4] After the restore point created, click on Close.

Note: - If your computer shows its turned off, make them ON. While doing this process you receive a message that asks whether you want to turn on system restore now. Click on Yes. Now move to further step In the System Properties dialog box, click to clear the Turn off system Restore check box, and then click OK, Repeat this step.