well you seem to have nearly the same setup like me:
Beige G3/DT/266, 160 MB Ram, 4 GB HD, 6MB ATI RagePro, Serial Modem. I Normally have 2 partitions. one for the os [512mb] and the other one for apps, documents, etc.... [3.5 GB]. for MacOS X I did a complete repartition: i did 2 partitions...