Sudden + massive loss of HD Space!!

So this is a weird one! I was using my computer lightly one night, the only things open were iTunes, Safari, Word, and maybe Azureus (but not dl'ing, only seeding).

It was off to the side as I was reading and i noticed the fan had been going for a while and was getting stronger, even though it there was nothing major going on. I checked it out and saw that my HD space had been reduced from it's normal 5 Gigs free to just over 1 free. And it was dropping every few seconds! It was as if I was dl'ing something very quickly, or importing DV footage, but the comp was doing nothing! (like I said, only seeding, not dl'ing).

Then a 'low disk space' warning popped up and I saw free space was down to around 600MB. I panicked and did a hard shut down. Now the problem is gone, but I still have no room and I cant find out why.

So my questions are:

1) Does anyone know what happened? (and by extension, how to get my free space back)

2) If not, is there an app out there that will tell me what massive files are lying around my computer so I can see if there's anything suspicious?

EDIT: I have already checked/repaired permissions. And the computer is a MacBook 2Ghz (not core2).

Thanks!

yellow said:

Or.. start with Terminal.app and type:

sudo du -h -d1 /

Click to expand...

What does this do? A rather ominous warning came up and asked for my password.

WildCowboy said:

It's not entirely uncommon for a runaway log file to eat up GB of disk space. Usually it's fine to just delete it, but it if it happens again, you'll want to look into the reason behind it.

To find huge files, use either OmniDiskSweeper or WhatSize.

Click to expand...

WICKED! I found it using WhatSize! It's a file called "windowserver_last.log"
and it's in /private/var/log/windowserver_last.log (over 4 Gigs!)

Any ideas what this is and how it got there?