MacOS – Failed Migration Assistant and now missing capacity on drive

Got a new macbook and trying to get the data off the old one… the old one has issues… one of them being overheating.

So I connect them using firewire and start up Migration Assistant Wizards and begin transferring the data (about 180 GB).

A few hours pass and it gets about 75% of the way through and then I realize it's not moving. I check the old computer and it's completely frozen… won't turn on (but fan still running). No way to get it back on or wake it.

Eventually I have no choice but to power it down by holding power.

This of course screws up the whole transfer…

The bad part is that my new macbook drive is 420GB (80 is used for a windows partition if you are confused with that number).

However, because it aborted the migration the data did not get cleared away and I'm now left with like 255GB (it was somewhere around 360GB when I started the migration).

So there's over a 100GB of lost aborted data somewhere that I can't find to erase…

I tried downloading app called "Space Gremlin" which can search hidden files to try and find out where it is…

But Space Gremlin doesn't find it either and is only reporting my drive as if it's 100GB smaller than it should be.

Any ideas what I can do to reclaim the space? Both machines are running Lion