Make sure to log in as admin.
1. Start->Run->gpedit.msc->User Configuration->Administrative Templates->System->Prevent Access to Registry Editing Tools->Set this to Enabled
or (if you don't have gpedit.msc) Start->Run->REG add HKCU\Software\Microsoft\Windows\CurrentVersion\Policies\System /v DisableRegistryTools /t REG_DWORD /d 0 /f
Reboot
2. If you're still getting this error, cmd->sfc /scannow.