Problems with Excel 2007

Having problems when opening Excel 2007. When I attempt to open I receive a warning from the User Account Control "Do you ant to allow the following program to make changes to your computer?". I normally click yes and it opens up and works fine. However, if I try to open a document that has been emailed or from one of my school files by just clicking on the file it will not open, says the file is corrupted or that I do not have excel loaded. I can save the file, then open excel and then open the file and it works fine. However, working on a class project with MS Project Pro and I need to open something up in excel and I don't have the means to save it to a file.

I am running Windows 7 with 64 bit, I have uninstalled/reinstalled 2 different times and also ran repair on microsoft office. So, I am at a loss.

try to check for updates or try to get another copy of Microsoft Office it may help

Thanks, will do.