Is it outlook 2002:

To resolve this problem, quit Outlook, rename the Resiliency registry key, and then restart Outlook. To do this, follow these steps: 1. Quit Outlook if it is running.
2. Press CTRL+ALT+DELETE, and then click Task Manager.
3. Click the Processes tab, and then verify that Outlook.exe does not appear in the list of processes.
4. Quit Task Manager.
5. Click Start, click Run, type regedit in the Open box, and then click OK.WARNING: If you use Registry Editor incorrectly, you may cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that you can solve problems that result from using Registry Editor incorrectly. Use Registry Editor at your own risk.

6. Locate and then click the following registry key:
HKEY_CURRENT_USER\Software\Microsoft\Office\10.0\Outlook
7. Right-click the Resiliency subkey (if it exists), and then click Rename.
8. Type Resiliency.old, and then press ENTER.
9. Quit Registry Editor.
10. Start Outlook, and then click Out of Office Assistant on the Tools menu.

In Outlook

Go to Tools
Go to Options
Go to Others
Click on Add-In Manager
Make sure you have

Exchange Extentions Commands and Exchange Extentions propertys page checkboxes are marked.

If not than mark them and try now.

Select Inbox and check in tools.

outlook 2003, not 2002(aka XP)

mkumar, the checkboxes are already marked.

For4 outlook 2003

1. Quit Outlook if it is running.
2. Press CTRL+ALT+DELETE, and then click Task Manager.
3. On the Processes tab, verify that Outlook.exe does not appear in the list of processes. If it does, click Outlook.exe and then click End Process.
4. On the File menu, click Exit Task Manager.
5. Click Start, and then click Run.
6. In the Open box, type regedit and then click OK.
7. Locate and then click the following registry key:
HKEY_CURRENT_USER\Software\Microsoft\Office\11.0\Outlook
8. Right-click the Resiliency subkey (if it exists), and then click Rename.
9. Type Resiliency.old, and then press ENTER.
10. Quit Registry Editor.
11. Start Outlook, and then click Out of Office Assistant on the Tools menu.

Only difference is with Registry key in outlook 2002 it is under HKEY_CURRENT_USER\Software\Microsoft\Office\10.0\Outlook

while in 2003 outlook it is under

HKEY_CURRENT_USER\Software\Microsoft\Office\11.0\Outlook

i followed your directions looking for the "resiliency subkey" ... but there wasn't one.
your directions for step 8(if it exists) doesn't have a (if it doesn't exists) option, therefore making step 11 pointless.

from that page:
>>
So by clicking Help -> About and then “Disabled Items” button, you should see the disabled AddIn listed there and you can enable it once again.
<<
 took a bit of reading from the author to get that one line of information.
Thanks for the link though.

Thanks ,

Is there any disabled item in help ..About of outlook?