the thing with the ps/2 to usb adaptors is that they work with usb 2.0 only not usb 1.1 and lower. the reason this is is that the adaptor requires more power then what a usb 1.1 and 1.0 port can provide. thats why back in the day most usb 1.0 and 1.1 devices needed 2 usb ports to be powered or they needed an external power source to work. i suspect u have a usb 1.1 port and so the ps/2 to usb adaptor wont work with the mac. what you would have to do is find a keyboard and mouse that is mac compatible just look for ones that say it works with a mac since not all usb keyboards may work with a mac