Hi, thank you for contacting JustAnswer.com. My name is Russell. I will do my best to provide the right answer to your question.
I think you may have to uninstall, then reinstall, the MP Navigator EX program.
First you should determine whether your Windows 7's 'System Type' is 32-bit or 64-bit.
Start - Control Panel - System [Information]
and look for the 'System Type' entry, which should be either 32-bit or 64-bit.
Then turn Off your MG3100.
Then go to
Start - Control Panel - Programs and Features
MP Navigator EX
in the programs list, then click on it once to select it, then do Uninstall.
Then restart your computer.
Then when it is restarted, go tohttp://www.canon.co.uk/Support/Consumer_Products/products/Fax__Multifunctionals/InkJet/PIXMA_MG_series/PIXMA_MG3150.aspx?type=download
and select, under
Filter On and Your Operating System
(if you have a 32-bit System Type) or
Windows 7 (x64)
(if you have a 64-bit System Type)
and of course
then scroll down to
MP Navigator EX
(which ought to be the second item on that list) and click on the big DOWNLOAD button next to it. Download that to your computer's hard drive, then save it there, then when the download is complete, locate the downloaded file, double-click on it, and do the program installation.
When the program installation is complete, turn On your printer again, open the MP Navigator EX program, configure it, specify your Destination Path (or similar) for your scans to go to.
And try it out again. See if that works properly.
If it does work properly, and you need no further information to clarify or help with this matter, please rate my Answer - favorably I hope - so that I may be paid for th ework I have done on your question. Thanks, ***** ***** luck.