Value Property (Windows Installer)
Specifies a registry value to search for on the target computer. If an exact match for the value specified in the Value property is not found, the registry search will return null.
If the Value property is left blank, the registry search will search for the default value of the key specified in the RegKey property. If the default value is null (appears as "Value not set" in the Windows Registry Editor), the registry search will return null. Additionally, if a key has no values assigned, the search will return null even if the Value property is blank.