Q: I have recently upgraded to Microsoft Office 2007 (student edition) with Windows Vista. When I try to open my Excel files, this pop-up appears:

"The file you are trying to open, filename.xls, is in a different format than specified by the file extension. Verify that the file is not corrupt and is from a trusted source before opening the file. Do you want to open the file now?"

There are three options: Yes, No and Help. When I click on 'Yes', the file is opened but is blank. When I click 'No', the file closes. When I click on 'Help', no solution is provided.

I have tried looking for a solution on the Web but none has worked.

Please help.

Cherish Koh

A: Have you tried using a different computer that has either Microsoft Office 2007 or 2003 installed? What are the results? While you try this, here are a couple of ideas you can try.

If your Excel files are online, that is, they are stuck in the Internet cloud in an e-mail message as an attachment in Hotmail or Gmail, move them offline to a USB drive. Try opening them locally instead of via the Internet.

The reason being there is now stricter security enforcement for opening files across the Internet. This is to curb the possibility of malicious software infection.

Update your Microsoft Office 2007 Home and Student 2007 edition if you have not already done so. Service Pack 2 is available, please visit: http://www.microsoft.com/downloads.

After a thorough search, I found a couple of conversations on the Internet that discusses a similar problem. However, the solution is not so easy to apply.

Here is the website URL where you can find details of making the necessary changes.

The instructions show how to force the opening by modifying the registry: http://www.itexperience.net/2008/03/17/excel-2007-error-different-format-than-specified-by-the-file-extension/.

An alternative is to convert all the older Office 2003 files into Office 2007 files.

Microsoft has a migration tool and you can read the details and download the program from: http://www.online-tech-tips.com/ms-office-tips/bulk-convert-office-2003-to-2007/.

Answer by M.K. Wong, an IT professional of nearly three decades and now a polytechnic lecturer, and Chester Chen, a recognised Microsoft Most Valuable Professional specialising in windows desktop experience

This story was first published in The Straits Times Digital Life.

For more The Straits Times stories, click here.