Any security settings you change on the network will affect ALL devices attached to it, so they will all need to be configured.
For a good discussion of Wireless security (and how to set it up), go to
http://www.cableforum.co.uk/board/showthread.php?t=8435.
We have an article that sums up the info in the thread nicely, but unforetunately, the Articles section is off line at the moment (due to Friday's upgrade).