To extend the inventory of the registry, there is a great tool (RegKeyToMOFv31.exe) to download from http://myitforum.com/cs2/files/folders/proddocs/entry152945.aspx
Start the tool and select the registry key you would like to add to the inventory.
Copy the syntax from the tool and paste into the "Added extensions" section of the configuration.mof located on the SCCM primay server install directory\Microsoft Configuration Manager\inboxes\clifiles.src\hinv (make a copy of the original file before you edit and save it).
Select the "to import in Admin/Agent settings...." tab oft the tool and save the information to a .mof file.
After that go to the SCCM console, Administration -> Client Settings -> Hardware Inventory -> Set Classes and then click Import..
Select the file you just created and verify that the new classes are added.
Run a hardware inventory action on a client and verify that the new registry values are added to the inventory.