HELP: Home networking questions

i am trying to make it possible to use our router between me and my room mate. we both have a big collection of movies and music. we want to make select folders viewable. i have set everything up and have everything running but i'm not sure how to lock down my mac a little better.

from HIS pc, it asks for a name and password, but only my (single user) mac account name and password work for this. he also can see my entire hard from my personal folder. i have mulitple hard drives and the secondary is where my stuff is that i want to share. to solve this i'm using sharepoint.

how do i lock up my primary hard drive?
how do i either give him his own name and password or make it so it doesnt ask for one?

i don't have 2 use sharepoint if someone has a better app or a native way to deal with file sharing within osx.


equipment:
g4 powermac, wireless usb adaptor, osx 10.4.11, 2 hard drives (2nd has 2 partitions and using hi-cap driver)

my roomate is PC w/XP

 

am i in the wrong forum?