Install Dropbox on both computers.

If you can only connect one computer to the internet at a time, that's OK.
Just do install it on each machine.
Connect the machine that you want to copy FROM, to the internet.
Put the files that you want to move, into the Dropbox folder.
You will not the little icon spinning around while it uploads the files.
Once done, connect the other machine to the internet
Go to the dropbox site and you will find all the files from the old machine are there.
Now drag them onto the new machine and that's it

P