Sure it's possible. USB adapter is probably the only usable solution. I've been successful with old Macs using Buffalo WLI-U2-KG54L (0411:00da) and zd1211b, vendor-based community driver, svn version. http://zd1211.wiki.sourceforge.net/ The speed will be limited to 11 Mbit/s because of the USB 1.1 interface on those iMacs. Risto