If you are using Windows XP and Outlook 2007, you will need to install PIAs (Primary Interop Assemblies) to ensure appears.
2. Click Download.
3. Click Run.
3. Click Continue.
4. Click Make New Folder.
5. Create a new folder called PIA.
6. Select the folder and click OK.
7. Open the folder and double click on the installer. This will automatically load and then close.
8. Close and reopen Outlook.