Now in Windows Explorer (Windows Key + E for a keyboard shortcut) select the pictures you want to resize.
Right-click your selection and choose Resize pictures.
In the Image Resizer dialog window choose the new image size.
I chose the Custom option as I want to resize images to the dimension of 800 x 600.
When the Ignore picture rotation option is enabled, pictures in portrait mode get resized will get resized (in my case) to 600 x 800 dimension. With the Ignore picture rotation option disabled my portrait oriented images would get a new size of 400 x 600.
Portrait oriented images are the ones that are images with greater height than width.
And voila, my .tif images are now in dimensions that are more suitable for sending via email or having them on my mobile device.