I googled this and found that sometimes its related to add-ons. The add-on that I believe I was having issues is the Adobe PDF Creator add-on. In order for me to remove the add-on I had to run the Excel 2007 as administrator. To do this go to C:\Program Files\Microsoft Office\Office12 folder. Right-click on Excel.exe and specify Run as Administrator (Only have to do this for Vista or Windows 7).

Then once in Excel click on the top left main button and then select the Excel Options.Click on the add-ons on the left. Then select Manage COM add-ons at the bottom. Deselect the Adobe PDFMaker and then select OK. Close Excel and restart and see if it fixes the speed of opening Excel files.

Also found this on the Internet:

Excel 2007 Bug Identiified

Since the upgrade to Office 2007, a bug has been identified on some computers that are running the new Excel 2007.

The issue that some people are experiencing:

• Excel files are not opening (or taking a long time to open) when double-clicking on the file or opening it from an e-mail attachment.

There is a very simple fix for this.

• Open Excel
• Click the Microsoft button (Round button top left)
• Click on the Excel Options button
• Select Add-ins on the left menu
• At the bottom of the screen make sure the pull-down window says excel add-ins
• Click Go
• Enable the look-up wizard
• Put a check mark beside Lookup Wizard
• Click OK

Please Note:
In some cases, Microsoft might mention that the add-on is not installed and ask if you want to install it.  Select Yes and let it run through the installation.  When it is finished, you will not get a confirmation, but the installation window will be gone.

Alternatively, a temporary fix is to minimize your Excel Window when it opens up blank.  Yes, that’s right!  Simply hit the minimize button and your Excel file will magically appear with the document fully loaded.  Don’t ask us why, this is just another Microsoft issue.

AMENDMENT:

After doing the stuff above I found another possible solution. Changing the file type association by adding a %1 after the /e. Thats fine if you are using Windows XP but Vista and Windows 7 does not allow detail changes like this in the file association. For me to do this I had to download a powertool that lets me do this. DOWNLOAD Installed it, restarted the PC and ran it. Went into the edit file type associations and ran the File Type Doctor. Looked for the .xls (using older 97-2003 files) and then added %1 after the /e in the open configuration.

AMENDMENT:

A newer blog I posted also has a fix if the files are located on a server (my example is a 2008 Server)