Please do NOT edit the registry without backing it up first, the results could be disasterous! 
Step 1: Back up the registry in Windows XP as follows:
a. Go to Start>Run then type %SystemRoot%\system32\restore\rstrui.exe. Click OK.
b. On the System Restore page, click "Create a restore point". Click Next .
c. On the Create a Restore Point page, type a name for the restore point you will remember. Click Create
d. Once created, click Close.
NOTE: If the restore is turned off, you will see a message box that asks if
you want to turn on System Restore. Click Yes. You will see a System Properties
message box, click to be sure the "Turn off System Restore" check box has been cleard. Click OK.
Once that is done, go through steps a-d.
If you are using Windows 7, go to this link to complete the registry backup step.
http://windows.microsoft.com/en-us/windows7/Back-up-the-registry
Step 2: Edit the registry in Windows XP/Vista/7
a. Click Start > Run
b. Type regedit in the text box
c. Click OK.