If you have Microsoft Internet Explorer as your default JPG picture viewer and they are displayed too large, you can change the way your browser displays pictures to automatically scale them to fit by taking the following steps:

1) From the toolbar above, select "Tools" / "Internet Options"

2) Select the Advanced tab.

3) Scroll down to the "Multimedia" section and 
check "Enable Automatic Image Resizing"

Now your pictures will be as large as your browser window.