Can't zoom out

My home computer got infected with a virus and my son decided to wipe it clean and install windows 7. I reinstalled Draftsight but am having problems. When I open a drawing it is zoomed in very far and no matter what I try I can not zoom out to see the whole drawing. Scrooling the mouse wheel only moves the drawing back and forth. Zoom Fit and Zoom Bounds do nothing. I have DS installed at work on Windows7 and it works perfectly.Does anyone have any suggestions? Thanks

Rob