I'm doing this for a friend who has Office 2003. She is trying to get the
office assistant to appear in her Excel file. She clicks on Help and then it
prompts her to install the feature as it is not currently installed. She
clicks okay and receives the following message:

Error 1311. Source file not found: C:\MSOCashe\All
Users\90000409-6000-11D3-8CFE-0150048383C9\5561404.CAB.
Verify that the file exists and that you can access it.

Please share with us what steps she needs to take to have the office
assistant installed and be able to show and use it.