Failed 10.6 Upgrade leaves 50GB+ of data??? Stumped...

Question

I attempted to run the retail 10.6 upgrade on my main internal 500GB on my MBP 17 (early 2007) with 10.5.8. At least 55Gb was available.
The install failed with a "Contact the manufacturer" message. I rebooted off the main internal drive which was still using 10.5.8 but there was only about 120MB available on startup.
Before upgrading there was at least 55GB available. After many attempts - I cannot locate the 58GB or so of data that the install process created.
I tried re-installing to see if it would "see" the incomplete install. The 10.6 installer did seem to see a "incomplete upgrade" but it would not proceed as there was not enough drive space.
I tried running Disk Utility from the 10.6 installer disk and DU says that it could not Repair the drive and to erase/initialize to use the drive.
I rebooted again back off the internal and after a very long startup - I am back up and running with 10.5.8 and again - a whopping 55GB of unaccounted for data. I erased about 6 GB of old stuff just to keep working on it. I have the drive backed up remotely but not a local copy. I want to just clone my drive but dont want to clone the 55GB of un-needed data.
In command line I ran:
$ df -h
It shows that /dev/disk0s2 has:
Size: 465 Gi
Used: 459 Gi
Avail: 6.1 Gi
Capacity: 99%
So I look at all my directories (inluding hidden) to see what they were taking up:
sudo du -hs ./*
The main ones being:
14G ./Applications
33G ./Library
3.9G ./System
335G ./Users
3.7G ./private
1.1G ./usr
(the rest were 10MB or less)
This adds up to just over 390GB.
I cannot figure out where the other 68GB is being used for the total reported 459GB that it says is being used.
How can I find where this data is?

Answer 1

I don't remember exactly where but, the installer places all the files it needs for the upgrade on the local drive and then swaps the files, reboots, loads the new files, etc. There are still other directories besides the ones listed below (and, not contained within /private) for instance bin, dev, home, net, sbin... But, it sounds like the files are still sitting on your drive and the system is just not able to make the swap. Likely, the issue Disk Utility reports is preventing loading the new software. I would say you're still looking at backing up, initializing the drive, reinstalling 10.5.x, then 10.6.x, then loading the updates, migrating your data... You've got a job ahead! Not hard but definitely time consuming.