More and more worm/viruses are using this barricading trick (disable task manager, cmd, msconfig, regedit)
The only way to clean the threat is to do it manually. The most important step is to regain regedit (ability to edit registry)
Option 1:
Go to Run, type gpedit.msc.
Goto User Configuration > Administration > Administrative Templates > System > Prevent Access To Registry Editing Tools = Disable
Option 2:
Download unhook.inf from Symantec. Install it.
Once you have regained registry, you can reverse the changes being made:
Refer to the sophos site under advance for the complete registry key list:
http://www.sophos.com/security/analyses/w32sohanap.html
Once you are sure everything have been removed, reboot
Finally do a system scan just to be sure.
All the best.