Disk space questions

I am new to MacOSX - having used Windows machines since 3.1. My question revolves around disk space. I have a Macbook Pro, Late 2011, i7 processor, 8GB RAM, and 128GB SSD, OSX 10.7.5. I am trying to clear some space so I can repartition for boot camp. My issue is that my Mac only reports 50GB of free space and 70GB used. I only have Office 2011 and Firefox installed, I keep all of my data on a server. I have run two disk space utilities - Disk Inventory X and OmniDiskSweeper - and both of those apps only report 17GB used and about 100GB availalbe.

So I guess the question is - why the discrepancy? I want to allocate 70 GB to my Windows bootcamp machine. Any help is appreciated!

Answer - really???

I found the answer after running the command

sudo find / -size +500000 -print

to find large files. Apparently time machine makes mobile backups onto the local disk whether you want it to or not? It was using my disk space. I would expect that would have been something I would have to have enabled. According to Apple's web site:

"Local snapshots are periodically condensed into daily or weekly snapshots to minimize the space used on your disk. If your disk is low on space, Time Machine stops creating new snapshots, and some or all existing snapshots may be removed to make space available for applications to use. If sufficient disk space becomes available again, Time Machine resumes creating local snapshots. This means your disk will have the same amount of available space as it would if Time Machine were not enabled."

Apparently that last statement is not ture they were using over half my disk! And with SSD's still "small" it does not make sense to enable this by default. I ran this command to disable mobile backups and then rebooted.

sudo tmutil disablelocal

Now my Mac shows only 15GB used and 97GB available - that's more like it.