Just the other day I erased some files from my HDD to gain some free space, I ended up with about 4 or 5 free GB.  But about 2 days later I got a system message saying that my hard drive was full and that i needed to erase files, I checked the hard drive info and it showed ZERO GB free!!!!

I had only downloaded a couple of songs and some emails, there's no way that would take 4 gigs of space!!!

Right now HDD info read about 100 free MB...

Could this be a virus?!?!?!?!?!

I know this is going to sounds really silly, but, did you empty the trash bin? :P

Do you use Photoshop? That can munch space due to odd bugs with the scratch file.

As far as we know there is no viruses out for OSx since it's a Unix based OS. The only thing I can think of is you must of filled up the drive with more then a few songs. Or some one broke into your system as used it as a hashserver but that would be kinda hard unless you have ROOT enabled and they got your password and you had a lot of ports forwarded.

I have photoshop but i haven't used it in months, i regularly empty the recycle bin, I only dowloaded 2 (TWO!) songs, both song are about 5 mb in size, root is not enabled (as far as i know... I made a separate admin account and run my ibook from a regular user account) most ports are closed...

I'm baffled.... a hdd hardware issue perhaps?

How do I search for files created from las thursday to last saturday?

Maybe this way I can find the offending files

if you have 10.4 you can use spotlight to check that out.  Or there is a very cool app called WhatSize.  It will tell you the exact size of folders in a hierarchical order so you can pinpoint obtrusive files.

http://www.id-design.com/software/whatsize/

My guess is that you have a fragmented HD.  There is a very nice command line daemon created for the hfs file structure that allows some low level analysis, hfsdebug...

http://www.osxbook.com/software/hfsdebug/

There is also a nice GUI for hfsdebug that makes things alot easier.  You will need the hfsdebug daemon for the GUI to function.  Just be sure to place it inside the same folder as the GUI app.

http://freenet-homepage.de/amichalak/page1/page1.html

If you would like to defragment your HD and optimize it, which would prob fix your issue, check out this app.  (its not free)

http://www.coriolis-systems.com/iDefrag.php

This will optimize your HD, defragment it and recreate your HD ToC which should fix a corruption of the ToC, which is most likely your issue. 

Let me know how it goes.

Just do a CMD + F in the finder and you will get a search windows that can do very specific searches.

what about archive and install?

Its more likely to be a problem with the directory of the drive than with the OS. An archive would probably not sort it, but its always worth trying before you erase the drive completely. Diskwarrior mght help you here.

If you want to know where the space is being taken up, just open a Finder window and set the options to calculate folder sizes. This trick should allow you to work out whereabouts this big file might be. If you find that the sizes you are given to not match the used space on the drive when ou add them up, its an error with the drive. It might be fixed by a reformat, or it might not.