If you have any idea of changing registry items be on safer side. Just take a backup before you doing changes to it. Here is the steps how to take backup for registry and how to restore registry items.
How to back up registry keys
1. Click on start and Click Run
2. Type regedit and click ok
3. On the File menu click Export
4. In the save in box, select the box at bottom according to weather you want to export all or only selected items from it.
5. Select the location where you want to select .reg backup file.
6. Click save
How to restore registry keys
Just move to the location where you saved your .reg file. Double click on the file and click ok to restore.