First off all u may be infected by virus .. do run a proper anti virus, anti spyware and malaware scans .. 2 remove it
and to enable disabled registry :
Click Start -> Run… and enter this command (all on one line) :
REG add HKCU\Software\Microsoft\Windows\CurrentVersion\Policies\System /v DisableRegistryTools /t REG_DWORD /d 0 /f