Excel 2007 : .xlsx extension files won't open on double click

[RichardMNixon]

Hi, I have an odd problem I've been unable to find elsewhere on the internet. I recently upgraded to Office 2007 from 2003. Any .xls files I have still work just fine as do any .docx and .pptx files. But for .xlsx files, they do nothing when I double click them. There's no error message, just nothing happens. To open them I have to open excel manually and drag the file into the window, which is really frustrating when trying to open files in email attachments since I have to save them first.

Does anyone know why Excel won't just open them on a double click? I set the default program to open it with as EXCEL.exe. I deleted all the registry entries associated with .xlsx but it didn't change anything. Any ideas you have would be appreciated.

Thanks,
Tim