If you do a search for OutlookSecureTempFolder in your Registry, all of the entries for all of the profiles will show up and you can tweak them as you wish-Provided that you are logged in an administrator on that machine. However, to be specific, there are entries in the HKEY_USERS that will also contain this. There should be a .DEFAULT and also some folders that have a long string of numbers and letters. These refer to specific profiles on that PC and is specific to one profile each. You would follow the same path within the folder with the long name and it will be there also. For Example: Say the users SID was S-1-2-34567abcdefg1a2b The folder for that particular user would be named that and you would go to:
HKEY_USERS\S-1-2-34567abcdefg1a2b\Software\Microsoft\Office\9.0\Outlook\Security
and you will find the OutlookSecureTempFolder string in there for that user's profile. Hope this is what you are looking for.