This worked for me and many others:
Here's a link to the forum:
[url]http://forums.microsoft.com/TechNet/ShowPost.aspx?PostID=1249654&SiteID=17[/url]
Here's the fix:
If this is your problem then you have to add the following to the
file types properties "%1" (also the quotes are necessary)
So open explorer -> Tools -> Folder Options -> File Types
got to the .XL?? extension click Advanced select the bold action ->
Edit and in the box under "Application used..." go to the end and add
the "%1" after the /e
so for the .XLSX Extensions Open command this becomes "<Installation
Folder>\Microsoft Office\Office12\EXCEL.EXE" /e "%1"
When it's the new action it should be "<Installation Folder>
\EXCEL.EXE /e "%1" /n
