Well I can tell you
If you have a canon 5D and have upgraded from XP to win7 then you will not be able to use your camera as the drivers for the 5D have not been updated to work with win7.
To enable your older canon camera to keep working you can by installing
Microsoft Virtual Machine and Windows XP mode onto Windows 7 pro or ultimate
Once you have installed these two pieces of software then you can install EOS Utility I found the older version that came with my 5D works OK and also install the canon WIA driver .
All works fine for me now you have to click on USB and canon camera in the toolbar menu to enable the camera in the XP enviroment