USB
something like this
Amazon.com: Medialink - Wireless N USB Adapter - 802.11n - 150Mbps -Windows 2000 / XP / Vista 64-Bit /128-Bit Windows 7 Compatible: Electronics@@AMEPARAM@@http://ecx.images-amazon.com/images/I/31e6ltwoVHL.@@AMEPARAM@@31e6ltwoVHL