Reference: regValExists
regValExists(RootKey, KeyName, ValName) returns True if the registry value ValName (a string) exists in the key named KeyName (a string) under RootKey. RootKey is "HKCU", "HKLM, "HKCR, "HKCC", "HKPD", "HKDD", or "HKU".
regValExists(RootKey, KeyName, ValName) returns True if the registry value ValName (a string) exists in the key named KeyName (a string) under RootKey. RootKey is "HKCU", "HKLM, "HKCR, "HKCC", "HKPD", "HKDD", or "HKU".