Wake on LAN (WoL) support is implemented in the motherboard of the computer. Most modern motherboards with an embedded Ethernet controller support WoL without the need for an external cable. Older motherboards must have a WAKEUP-LINK header onboard and connected to the network card via a special 3-pin cable; however, systems supporting the PCI 2.2 standard coupled with a PCI 2.2 compliant network adapter typically do not require a WoL cable as the required standby power is relayed through the PCI bus.
Wake on LAN must be enabled in the Power Management section of the motherboard's BIOS. It may also be necessary to configure the computer to reserve power for the network card when the system is shut down.
In addition, in order to get WoL to work it is sometimes required to enable this feature on the card. This can be done in Windows from the properties of the network card in the device manager, on the "Power Management" tab. Check "Allow this device to bring the computer out of standby" and then "Only allow management stations to bring the computer out of standby" to make sure it does not wake up on every single network activity that occurs.
For more info and software check here:
http://en.wikipedia.org/wiki/Wake-on-LAN
PS. It does NOT work very well with wireless LAN cards, only few Wireless cards support it. So your VISTA computer should be no problem if the motherboard and NIC support it. Don't forget to enable it in the BIOS!
PS. As a rule, PCMCIA and USB NICs do NOT support it, most laptop NICs don't support it. Usually only desktop PCI cards do.