Hard Drive Space

I have had my IMAC for 6 months. I am running MAC OS X 10.5.8.
The Macintosh HD "GET info" claims there is 472.4GB used out of 595.9GB. I shouldn't be anywhere near this. When I select Get Info from anything within Macintosh HD there are no surprisingly large folders.
After looking at several sites and threads in this forum, I ran OmniDiskSweeper and it calculates 62.0GB total. A big difference from 472.4GB.
I'm new to the MAC OS and I can't figure out how to free up this space. Anyone have solutions?

Open Terminal from your Utilities folder and type the following command, then copy and paste the results back here. Be sure to wait for it to finish (you'll get the prompt back again); it might take a bit depening on how many files you have. That will help in finding where space is being taken up.

Thanks for the reply here is the data FYI There are four users, do I need to repeat this for all users?:
todd-wilkeys-imac:~ Todd$ du -hd1
4.0K ./.cups
260K ./.Trash
1.1G ./Desktop
107M ./Documents
721M ./Downloads
541M ./Library
247M ./Movies
264M ./Music
19G ./Pictures
8.0K ./Public
72K ./Resumes
56K ./Sites
22G .
todd-wilkeys-imac:~ Todd$

Hmm, not necessarily. Do you have an administrative account? If so, type the following commands and let me know the output.
That will show how much space each user is using, and hopefully we can narrow it down from there. You'll have to type your administrative password for the second command; that's just because you aren't allowed to access other users' files by default. However, if you are an administrator, it will save you from having to log in as each user to repeat the command. If you aren't an administrator, repeating it would help, if you're willing.

I ran the original du -hd1 logged in as each user. Here is a clip of one of them.
8.0K ./Public
40K ./Sites
389G .
todd-wilkeys-imac:~ Morgan$
The 389G. caught my eye naturally. I used omni disk sweeper in that account and found a folder called recovered videos. There was one .avi inside. I played it and it was a 29 second video from a cell phone. I found the original in the videos folder and it was 280mb. I deleted the recovered videos folder along with the 389GB .avi and now my system is just under 100GB total.
I am calling this fixed. Thanks for your help.

Wow, that's one huge video. Glad you got it fixed.