I just got a new computer at work. It runs Windows Vista (finally) and Office 2007. This is a completely fresh install from a corporate deployment image (no prepackaged adware). The deployment image did not have Office included since we run a mix of 2003 and 2007 here currently. So the Office installation is even more fresh.

Despite this, I ran into a really weird bug. Anytime I tried to open Excel files by using Explorer file association (ie, double clicking on the target file, instead of using File->Open menu within Excel), I would get the following error...

Screenshot of Excel 2007 throwing a file not found error

My first thought is permissions. I double checked. They were correct. Okay what's the problem? I opened the file from WITHIN Excel. It worked! Very strange.

I searched the google on the internets and found this post. Apparently, there's an advanced setting in Excel that can interfere with file association opening. Very odd. Click on the office "pearl" (the circle button in the upper-left corner of Excel), then click on "Excel Options." From there, click on "Advanced," scroll down to "General," and uncheck "Ignore other applications that use Dynamic Data Exchange (DDE)." (March 21, 2008 - Thanks to Shrivmather, in the comments below, for pointing out a mistake in the preceding paragraph. It has been corrected.)

Screenshot of Excel 2007 settings

I'm not sure I understand entirely why this setting prevents files from opening by association, throwing a "File Not Found" error. Maybe somebody can explain this to me? Well, the solution works, so mystery solved here...