To register go to HELP and then click on BUY. The reg box appears. You have to enter each section of the reg code separately. After entering the reg code i got an error box so it is still in 30 day trial mode. The image will re-size in pixels but there is no option to change the DPI. There are a few useful FILTER tools to change the image such as Sharpen etc, but sadly too limited for me as most of these features are standard in Photo Commander, Zoner Photo Studio etc.