When you are using a lot of computers with large files, BitTorrent works best. Of course, you may not want to use a public tracker. Luckily, uTorrent has the option to act as a tracker. This Instructable only covers operating this on a LAN, but you can use port forwarding if you wish to share the files with people on the Internet. This is not covered in this instructable though.
When to Use this MethodBitTorrent is made for transferring large files to a large number of computers. If you only need to transfer files to a small number of computers or the files are very small, it is much easier and quicker to use a flash drive or other removable media.
Note: I will not be explaining the basics of BitTorrent in this instructable. Some previous experience is recommended. Also, this is meant for LEGAL use such as home videos or sending large amounts of your pictures to other home computers. I am not responsible if this is used in an illegal way or if you somehow mess up your computer or network.
Network Switch Picture by Wikimedia Commons user Zuzu