There are many ways:
-Use an USB key, or an external hard disk
-Connect two computers by LAN (or by WiFi, or by internet, if you are not concernet about privacy), run an FTP server on one, and upload/download whatever you need
-Open one computer, take the hard drive (of course, turn it off before!), mount it into an USB socket and connect it to the other computer
-Connect two computers by a LapLink cable
-Burn a CD/DVD on one computer, read with the other
-Use a remote file hosting service.