I can't get Excel files to open in 2010 anymore when I double-click on them. They always open Excel 2007, instead.

I installed Office 2010 on my Windows 7 Ultimate machine. Fine, no problems. Then I had to install Excel 2007. Now, every xlsx and xlsm file starts up 2007 when double-clicked instead of 2010. Set Associations in Control Panel is of no help:

I can start both 2007 and 2010 from the Start menu; they're both listed in a Microsoft Office folder there. But when I search (Windows Start/Search programs and files) for EXCEL.EXE on my computer,only one is found. It's in Program Files/Microsoft Office/OFFICE14. That is the file to which xlsx and xlsm extensions are associated (Set Associations in Control Panel) and there is no other to which those extensions can be associated. To add to this Alice in Wonderland story-line, I don't see Office 2010 in Control Panel/Programs and Features, though I do see Microsoft Office Ultimate 2007.

Ultimately, I'd like to have Excel 2010 come up by default when I double-click any Excel file. In the process of getting there, I'd like to understand the environment I described above, which right now seems nonsensical to me.

Thank you for any help.