I have a power mac g4 with 10.4.3 that I ran omni disk sweeper on after having few start up issues. I got it up and running but I still have major disk space being used and I already deleted alot of useless files (or so I thought) I'll list what the Omni Disk Sweeper listed, if anyone can help me decipher what CAN be deleted without screwing things up... Thanks! 
SHANNON'S HD -------- 2.3 GB FREE, 16.2 GB USED, 18.6 GB TOTAL
SHANNON'S HD - 15.7 GB (IS WHAT IT SAYS AT TOP OF THE LIST)
7.0 GB USERS
3.3 GB LIBRARY
2.7 GB APPLICATIONS
1.2 GB SYSTEM
455.7 MB USR
394.0 MB VM STORAGE
280.2 MB SYSTEM FOLDER
101.6 MB APPLICATIONS (OS 9)
88.9 MB PRIVATE
9.6 MB NAVMAC800QSFILE
4.3 MB BIN
4.1 MB MACH_KERNEL -----WHICH I HAVE ANOTHER Q ABOUT
2.3 MB SBIN
1.8 MB DESKTOP DF
THERE ARE OTHER KB'S THAT I DIDN'T LIST- AND IF YOU NEED MORE INFO ON ANY PARTICULAR FILE(S) LET ME KNOW
SHANNON'S HD -------- 2.3 GB FREE, 16.2 GB USED, 18.6 GB TOTAL
SHANNON'S HD - 15.7 GB (IS WHAT IT SAYS AT TOP OF THE LIST)
7.0 GB USERS
3.3 GB LIBRARY
2.7 GB APPLICATIONS
1.2 GB SYSTEM
455.7 MB USR
394.0 MB VM STORAGE
280.2 MB SYSTEM FOLDER
101.6 MB APPLICATIONS (OS 9)
88.9 MB PRIVATE
9.6 MB NAVMAC800QSFILE
4.3 MB BIN
4.1 MB MACH_KERNEL -----WHICH I HAVE ANOTHER Q ABOUT
2.3 MB SBIN
1.8 MB DESKTOP DF
THERE ARE OTHER KB'S THAT I DIDN'T LIST- AND IF YOU NEED MORE INFO ON ANY PARTICULAR FILE(S) LET ME KNOW