Would have thought any software would use the printer driver... so maybe it is something wrong with the driver, rather than windows photo viewer. Have you looked on the printer manufacturers website to see if they have an updated driver for Win7?
However the add-on driver is July 2013, so not as new as the Win8 driver. Thus try the more recent driver first... see if it installs, detects the printer. If it gives problems, then try the older driver.
I couldn't install the very latest one as it said i don't have x64 or bit?
So i went for the 2nd newest, which installed fine, but the prints are still faded, and lots of crazy lines which weren't there before. This really is a puzzle, it's a pita to boot up my old pc to do printing, as it's rarely used. do you have any other ideas? I expect a nozzle check and deep clean (which i did yesterday) might help the lines, but the faded pics?? hmm I do not like windows photo viewer.!