If you are connected via the same network then don't send it via the internet or usb or that crap
, why not just send it directly to the other computer using the fast speed of your network!
If your using Windows XP, click on "my network places"
and see if you can see your other computer in there, if not you are going to have to setup both computers for sharing using the "network setup wizard" which u'll beable to find in "my network places" on the left hand side (windows xp). To share a folder right click on the folder and click "sharing and security" and the options are all in there