Hi Bob,

It sounds like there might be an issue with the default file location for Excel. Here are some steps you can try to resolve the issue:

1. Open Excel and click on File in the top left corner.
2. Click on Options at the bottom of the left-hand menu.
3. In the Excel Options window, click on Save in the left-hand menu.
4. Check the Default file location field to see if it is pointing to a valid location. If it is not, update it to a valid location.
5. Click OK to save the changes and close the Excel Options window.
6. Close Excel and reopen it to see if the error message still appears.

If the above steps do not resolve the issue, you can try repairing or reinstalling Microsoft Office. Here's how:

1. Close all Office applications.
2. Open the Control Panel and click on Programs and Features.
3. Find Microsoft Office in the list of installed programs and click on it.
4. Click on Change at the top of the window.
5. Select Repair and click on Continue.
6. Follow the prompts to complete the repair process.
7. If the repair process does not resolve the issue, you can try uninstalling and reinstalling Microsoft Office.