Excel File save in office 2007 format

Hi All,

I'm developing a small application that creates Excel files with user details. I'm developing this in vb.net 2008 express edition under Windows XP SP2 and with Office 2003.

My target PC is running Windows Vista. I'm able to run my program without any problem and even the Excel files get created without any problem on this PC.

However, the problem is when I try to open one of these created files in Vista, I get a message like below:

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

If I click yes, it opens up properly. This is a headache as it opens up in my developing PC without any hassle. I'm sure its something to do with the Excel reference I've made in my PC (which is running Office 2003).

How best can I save this file so it opens up in Excel 2007 without the above message.

THANKS IN ADVANCE