Registry editor is disabled on windows machine (Regedit.exe)

Problem Description: User cannot run regedit.exe as command to open registry editor.

Cause: There are different reasons for it please look below for more info

Resolution:
There are different reasons why you could be seeing this issue:

1. Because someone changes the group policy.
To fix this issue run the following command from the RUN box:

REG add HKCU\Software\Microsoft\Windows\CurrentVersion\Policies\System /v DisableRegistryTools /t REG_DWORD /d 0 /f

OR

use group policy editor: gpedit.msc from run box and then look for policy called "Disable registry editing tools " set it to not configured state and restart computer

2. This could also be caused due to different viruses/malware

to fix this there is a nice script from Symantec just use that
http://securityresponse.symantec.com/avcenter/venc/data/tool.to.reset.shellopencommand.registry.keys.html

even I could export my shell commands configuration in registry and send you as a TXT file but I think Symactec tool already does the trick for you.