Moving multiple files on latest MacBook

Well, feeling rather silly - BUT - I am having trouble moving a series of files from one folder to another on wife's new MacBookAir, updated to latest OS. With my older Macbook, I would highlight files to be moved, press the lower left corner of the magic pad and just drag to new folder. Now with new Macbook, after highlighting files to be moved, when I press lower left corner of magic pad, all selected files, except the last, go unselected. What do I need to press in order to move files?