These types of problems drive me nuts, too. If you have solved the problem, I would like to know what you did. If you didn't, I was wondering if you would:
Click "Start"
Click "Pictures"
Double-click the "Sample Pictures" folder (or something else if it is not there)
Right-click one of the pictures (preferably a .jpg)
Click "Properties"
Check what program the picture is set to open with
Click "Change"
Set it to "Windows Media Center"
Back out and check the sequence again to see if that picture then displays
If a picture has been set to open with a specific program, changing the default program for that file type doesn't always apply the change globally to all existing pictures, only to new ones. I'm not sure about Win 7 yet, but it would be interesting to check one picture, as outlined above, and see what the result is. It might provide a clue ... or not! Good hunting.
Click "Start"
Click "Pictures"
Double-click the "Sample Pictures" folder (or something else if it is not there)
Right-click one of the pictures (preferably a .jpg)
Click "Properties"
Check what program the picture is set to open with
Click "Change"
Set it to "Windows Media Center"
Back out and check the sequence again to see if that picture then displays
If a picture has been set to open with a specific program, changing the default program for that file type doesn't always apply the change globally to all existing pictures, only to new ones. I'm not sure about Win 7 yet, but it would be interesting to check one picture, as outlined above, and see what the result is. It might provide a clue ... or not! Good hunting.