PXE = Preboot eXecution Environment
PXE boot server is a combination of DHCP and TFTP server.
By using PXE stations can boot on LAN even without a harddisk.
TFTP (Trivial File Transfer Protocol) is a simple protocol for transferring files, only reads or writes files from or to a remote server on UDP/IP Port 69
You can find both servers in a one file exe in the app here : http://tftpd32.jounin.net/