Mike:
Thanks. I tried what you suggested, and it's possible to get it to work, however it's a little different than before, and requires some setup and a few additional steps.
If you right-click on a folder, there is no "Open With" option, only the "Open" option is visible. So you have to go down one level further, select and image, and then when you right-click you will see the "Open With" menu. Hover the cursor over that, option, then when the options appear to the side, scroll to the bottom of that list, and click on "Choose default program." In the resulting menu, first be sure that the option box to "Always use the selected program to open this kind of file" is "unchecked" as you probably don't always want to have your JPEG or RAW files open in Photo Mechanic. ;-)
As Photo Mechanic is unlikely to appear in the list of "Recommended Programs" (or even "Other Programs") you'll need to click the "Browse" button and then locate Photo Mechanic. This dialogue will generally default to the 64 bit programs (if you have installed the 64-bit version of Windows 7), so you'll need to go up a level and locate the "Program Files (x86)" folder since Photo Mechanic is a 32 bit program. The path should be something like
C:\Program Files (x86)\Camera Bits\Photo Mechanic 4.6\
Locate the executable file - "Photo Mechanic.exe" - and select that item. Then click on the OK button in the browse dialogue and then OK again in the "Open With" dialogue.
In order to use you do have to navigate down to the image level (rather than right-clicking on the folder), and then choose "Open With" and choose Photo Mechanic from that flyout menu.
Thanks for sharing as I didn't think that would work. It's certainly a few more steps, than the option that's available under Windows XP, but it's better than not having it at all.
David