garage band for older macs

My friend has a 2003 Mac and was told that she can't use Garage Band. I found that hard to believe so I thought I would come here to the experts for real results. Does anyone know how she can use Garage band?

Thanks

Oh, and I have been trying to record "karoke style" just fooling around with it, but I keep hearing those clicks (metronome?) and don't know how to turn them off, they are coming back in the recording too, any suggestions?

thanks
ruez