COMPUTER TRICKS AND TIPS

Many viruses disable the access to the registry so that we can't remove the virus entries in the registry. In these cases you can download the following file UnHookExec.inf. After downloaded, right click on the file, and select Install.

You can enable it manually by editing the group policy editor. Go to Windows > Run > gpEdit.msc
Go to User Configuration > Administrative Templates > System > Prevent Access to Registry Editing Tools. Disable it. You should be able to open regedit now.

Source: Tool to reset shell\open\command registry keys