Moving files from G4 to iMac?

I have a G4 that I bought in 2001-

512 MB RAM; 466 MHz Processor; running OS 10.3.9

I want to buy a new iMac but I'd like to be able to use the old G4 as an external hard drive. Is that possible?

If not, how would I go about transferring the pictures, music etc. that I've collected on the G4 to the iMac?

Thanks!