Deleting Registry Keys and Values
To delete a registry key with a .reg file, put a hyphen (-) in front of the RegistryPath in the .reg file. For example, to delete the Test subkey from the following registry key:
HKEY_LOCAL_MACHINE\Software
put a hyphen in front of the following registry key in the .reg file:
HKEY_LOCAL_MACHINE\Software\Test
The following example has a .reg file that can perform this task.
[
-HKEY_LOCAL_MACHINE\Software\Test
]
To delete a registry value with a .reg file, put a hyphen (-) after the equals sign following the DataItemName in the .reg file. For example, to delete the TestValue registry value from the following registry key:
HKEY_LOCAL_MACHINE\Software\Test
put a hyphen after the "TestValue"= in the .reg file. The following example has a .reg file that can perform this task.
HKEY_LOCAL_MACHINE\Software\Test
"TestValue"=-
http://support.microsoft.com/kb/310516