Please try this (borrowed from Quietman7)
This step involves making changes in the registry. Always back up your registry before making any changes.
Go to Start » Run and type: regedit
On the left side, click to highlight My Computer
at the top.
Go up to File » Export
Make sure in that window there is a tick next to "All" under Export Branch.
Leave the "Save As Type" as "Registration Files".
Under "Filename" put RegBackup
Choose to save it to C:\
Click save and then go to File » Exit.
Or you can download and use ERUNT
which is an excellent free tool that allows you to to take a snapshot (backup) of your registry before making changes and restore it when needed.
Click on the link below:http://www.kellys-korner-xp.com/xp_tweaks.htm
Scroll down to #275 and click "Lift Restrictions - TM, Regedit and CMD" in the left column. Go to File, choose "Save page as" All Files and save regtmcmdrestore.vbs
to your desktop. Double-click on that file to allow the script to run and reboot when done. Since the script modifies certain registry settings your anti-virus package may warn you about it. Ignore the warning and allow it to run.