I am updating this post for Outlook 2010 and Outlook 2013.
The original post covering previous versions of outlook can be found here – http://blog.powerbiz.net.au/registry-hacks/where-is-the-temporary-outlook-folder/
For Outlook 2010, the registry location which shows the location of the Outlook Temporary Folder is HKEY_CURRENT_USER\Software\Microsoft\Office\14.0\Outlook\Security.
For Outlook 2013, the registry location which shows the location of the Outlook Temporary Folder is HKEY_CURRENT_USER\Software\Microsoft\Office\15.0\Outlook\Security.