Never use a screwdriver for a hammer.
# How is the hard drive partitioned
fdisk /dev/hd<X> -l
# How much free drive space
df -h
# Show disk usage by current directory and all subdirectories
du | less
# What takes up so much space on your box
# Run from the directory in question and the largest chunk shows up last
find $1 -type d | xargs du -sm | sort -g
Look at
man <command> or
info <command> for the flags I used and for other options you can use for bash commands.