1) Exit Excel 2007.
2) Start Registry Editor.
3) Locate and then click the following registry subkey:
HKEY_CURRENT_USER\Software\Microsoft\Office\12.0\Excel\Security
4) On the Edit menu, point to New, and then click DWORD Value.
5) Type ExtensionHardening
, and then press ENTER.
6) Right-click ExtensionHardening
, and then click Modify.
7) In the Value data box, type 0, and then click OK.
The following list contains the value data settings that are appropriate for the ExtensionHardening
setting:
0: Do not check the file name extension and the file type, and bypass the function of the warning message.
1: Check the file name extension and the file type. If they do not match, display the warning message.
2: Check the file name extension and the file type. If they do not match, do not open the file.
Note: The default value data is 1. When the value data is set to 1, the behavior becomes the same as when no registry value is set. When the value data is set to 0, the file name extension and the file content are not checked in all situations. It is not recommended bypassing this function.
8) On the File menu, click Exit to exit Registry Editor.
Go to http://support.microsoft.com/kb/211494 and it will give a very clear explanation of how to make it so Excel opens the file. I searched on: "Excel 2007 'There was a problem sending the command to the program'" since that was the error message.
Open the Excel application. Here are Microsoft's instructions from that link - very simple to follow!
Microsoft Excel 2010
Click the File tab, and then click Options.
Click Advanced, and then click to clear the Ignore other applications that use Dynamic Data Exchange (DDE) check box in the General area.
Click OK.
Microsoft Office Excel 2007
Click the Microsoft Office Button, and then click Excel Options.
Click Advanced, and then click to clear the Ignore other applications that use Dynamic Data Exchange (DDE) check box in the General area.
Click OK.
Microsoft Office Excel 2003 or earlier versions of Excel
Click Options, on the Tools menu.
Click the General tab.
Click to clear the Ignore other applications that use Dynamic Data Exchange (DDE) check box, and then click OK.
Even if the option Ignore other aplications that use Dynamic Data Exchange (DDE) is already clear (false), click to enable and then click to disable.
After you do this, you should be able to open workbooks by double-clicking them in Windows Explorer.
Best Answer
You don't say what OS you have, so your mileage may vary. On XP, the usual way used to be from the command line:
However, on my Win7 system this makes no difference. (like you I have 2003, 2007 and 2010 installed, 2007 is default for me and does not change with above commands, run as user and as admin) Next best option usually is control panel > programs > add/remove (again exact route depends on your OS here) > choose the Office install you want and do a change > repair on it. This can take a while, but I just did it on 2010 and it worked, this is now my default.
With the benefit of hindsight, install the one you want to be default last, repair effectively winds back the clock and installs a previous one again, making it "last".
(have to go run it on 2007 now since that is what I really want to be default for Excel at the moment since I am teaching some courses on it next week)