Wake550 allows you to wake a sleeping computer from over a LAN. Simply type the MAC Address into the dialog box labeled "Hardware Address". To find the MAC Address, use the "Network Utility" program found in the Utilities folder on the target machine, assuming it is running Mac OS X. The different MAC Addresses are listed under the info tab. Theoretically the program should wake Windows machines as well, assuming the Windows machine has a Wake-On-LAN compatible ethernet card. It will not wake a computer that is only connected to the network through Airport, as the Airport antenna of the target machine will power down while asleep.