Excel 2007 error: Different format than specified by the file extension

I receive the error shown below everytime I double click to open and excel file.  I found the following info on the internet:
"In some cases after upgrading to Excel 2007, you may get the following error:
The file you are trying to open .xlsx is in a different format than specified by the file extension. verify the file is not corrupted and is from trusted source before opening the file. Do you want to open the file now?

This errors particularly occurs when you’re trying to open an XLS file (Excel 2000-2003) with Excel 2007. In most cases, the problem can be solved by defining MIME types and associating them with extensions."
This is exactly the case.  I have Excel 2007 and the files I typically work with were exported from a web application and saved as Excel 2000-2003 files.

What does it mean by defining MIME types- how do I do that?  I would like to resolve this.
Who is Participating?
I wear a lot of hats...

"The solutions and answers provided on Experts Exchange have been extremely helpful to me over the last few years. I wear a lot of hats - Developer, Database Administrator, Help Desk, etc., so I know a lot of things but not a lot about one thing. Experts Exchange gives me answers from people who do know a lot about one thing, in a easy to use platform." -Todd S.

I believe you have to right click the item and hit "Open with", then select always open with this program.

Experts Exchange Solution brought to you by

Your issues matter to us.

Facing a tech roadblock? Get the help and guidance you need from experienced professionals who care. Ask your question anytime, anywhere, with no hassle.

Start your 7-day free trial
snyperjAuthor Commented:
Close enough.  Problem actually is that it is an html formatted doc with an .xls extension.
It's more than this solution.Get answers and train to solve all your tech problems - anytime, anywhere.Try it for free Edge Out The Competitionfor your dream job with proven skills and certifications.Get started today Stand Outas the employee with proven skills.Start learning today for free Move Your Career Forwardwith certification training in the latest technologies.Start your trial today
Microsoft Excel

From novice to tech pro — start learning today.