MAC OS FULL 20gb of hidden files?

My HD is getting filled with hidden files. If I compare it with my 1st Time Machine back up, it's all the same but with 20Gb extra... If i "get info"of each files (applications, library, system ) it is all the same except "users"so i open "users", there is 2 files, "shared" and "me" NOW look: if i open every folder inside "me" (application, desktop, documents,download...) IT IS ALL THE SAME AMOUNT OF GB BUT IF I "GET INFO" OF THE "ME" OF THE 1ST TIME MACHINE BACKUP AND TODAY THERE IS 20GB DIFFERENCE!
My Question: what is it? How can i see these 20gb of files and remove them???
THANKS!

did i mentioned that i have a MBP quadcore with Lion

First bit of advice. Generally, unless you know exactly what your deleting, leave everything inside the Library folder alone, unless you want to mess up your machine.

Second, dont mess with Time Machine back ups for the same reason.

Try deleting your caches in browsers. Are you sure these files are actually system files? you havent downloaded anything new?

Also look carefully at the contents of the Documents, Movies, and Music folder. I don't make it a habit of saving documents in my user folder so I never use them. Unfortunately, from time to time some program will default to there and I accidentally save a large file without realizing it.

It's likely an accumulation of cache files and regular data. Any chance this 20 GB is hiding in your trash? I also occasionally see the trash not properly empty, resulting in hidden trash files that never disappear until they're manually removed via Terminal.

You might try downloading and running the program What Size, which will tell you exactly where and what this extra data is. Additionally, try running Yasu or Clean My Mac to remove unnecessary cache and junk files.

i have ran cleanmymac application to remove all kind of unwanted files but still... 20 Gb of unknown stuff... The funny thing is: when i check the size of the folder called "me" (MAC OS / users / shared folder or "me"folder) there is 27Gb and the very same folder in my 1st backup (when the machine was just re-installed 3 months ago) there is 7Gb... (w.t.f.???)
Ok, i re-installed my whole machine 3 months ago because Lion was bugging; and now i have to do it again? Please God, save me!... (joke)

If you are using Time Machine on could hidden local backups be the issue? Hidden local backups with Mac OS X Lion filling up your MacBook hard disk! - 0x4e71

EDIT The link opened for me but the formatting was all messed up. Apparently that post has a new address http://blog.valerio.de/post/19238158977/hidden-local-backups-with-mac-os-x-lion-filling-up-your

@Slydude

Check that link as it won't open. Can you verify?

Thanks Slydude, yes indeed it is a hidden local backup.
I did the "sudo tmutil disablelocal" + password in the terminal, reboot a couple of time but still there...
Then i did the sudo thing again, reboot again, no luck...

Please look at the status of my 2 partitions HD (attached)

Check out this post Lion’s local backup devours disk space. The author reports getting rid of the folder with a combination of a Terminal command to make the folder visible and Clean My Mac to actually delete the locked file from the Trash.

I don't have Clean My Mac installed but Onyx has a similar function if I remember correctly.

Great post, thank you Slydude. I did what he did, and deleted the mobilebackup but it didn't help. What confuse me is with my istat menu bar icons, when i turn on the time machine i can see the mobilebackup full of 50+ Gb I also found an hidden library of 35Gb... Ah la la... I may just reformat again and never turn this Time Machine again (from the menu bar i can chose to backup without having to turn on the time machine slider)
Thanks antways

PROBLEM SOLVED!!!
It drove me nuts, so what i did is restore my computer to the 1st backup after installing all my applications then i updated the data that i had saved. It was fast, now my HD has 34Gb free instead of....4

So i made a tutorial to remember for next time; I thought i could share it here...

restore the computer to "1st day pristine state"

1) Make sure you have done a Time Machine Backup on your external HD right after your all your applications are installed and updated, permissions verified, the whole package rebooted. Then NOTE the ref. of his precious back up and NEVER let Time Machine fill up your external HD and delete the older backup. You want to control that, in order to NOT delete that particular backup

2) make sure you have disable the automatic mobile backup by typing in the terminal: sudo tmutil disablelocal and never turn on the Time Machine switch, you can backup manually by clicking on the time machine icon on the menu bar

3) save tour data, bookmarks, contacts, preferences of some upgraded applications (just in case)

3) Turn off your computer, turn it on and press / hold the option key. Choose the recovery disc and restore from the backup you have saved (1st day pristine state)

4) when this is done, update your applications and install new ones if needed, verify permissions, reboot and make a new backup with Time Machine. Take note of its ref. It is your new "1st day state" backup you want to save for the next time

Well, i am not a computer gig, this tutorial may be far from perfect but it did worked for me and it allow me to always have a fresh and clean computer with little effort
Hope it help some...

Glad to know you that information was helpful. My Time Machine drive was disconnected the other day for a day or two before I remembered that it was off. I will be checking my drive later to make sure I don't have the same problem.