How long does a (fsck_hfs) cron job run?

Hi everyone,
I was wondering how long cron jobs tend to run. The reason I ask is that I've found my g4 powerbook to be working really hard (70-90% CPU) on a process called "fsck_hfs" for about the past 15 hours via the activity viewer.

I'm guessing this is something the computer started automatically, but am wondering how long I should expect it to continue?

Is there a way I can get more info on cron jobs, or the fsck command that is running in particular? Is is better to wait it out, or does it matter if I reboot my computer/end this process before it comes to its own completion?

Thanks for the help,
Owen

Something is wrong, hopefully not forever...

I killed the process that was running via Activity Monitor, and then ran a

....$ sudo fsck_hfs -l /dev/disk0s3

which went about its way for a bit, and in less then ten minutes it returned the error:

** Checking volume information.
Invalid volume free block count
(It should be 3425368 instead of 3429722)
** The volume Hedwig needs to be repaired.

I repaired permissions, there were a few off, including DVD Player, some widgets, and a handful of items in /usr/lib/php/ folders.

I then attempted to verify the disk via Disk Utility, just to see what it said before going off to single user mode or booting from DVD and running the fsck again.

Disk Utility said about the same thing, except it read:

Invalid volume free block count
(It should be (It should be 7 instead of 3429751)
The volume Hedwig needs to be repaired.

Error: The underlying task reported failure on exit

[Including the funny word repetition]

I'm now off to try a little bit more serious methods of recovery, and will report back as to how the issue resolves.

The Disk Utility report leads me to believe that it could be related to the obscenely large amounts of virtual memory OS X is using....over 10Gb sometimes. (I have an 80Gb Hd with 12 free- I always thought 10 percent was a safe percent to keep free for the OS, but should it be more like 25?)

I just about have enough space on an external drive to backup my laptop and do a fresh format, does this seem like it would be a good idea at this point or is this the sort of problem that I can resolve and keep from recurring without resorting to that method.

Thanks everyone,
Owen

Thanks

::Try fsck. I linked to it earlier. As ever, keep everything backed up.
::Having said that, fsck is a pretty safe process.

Thanks for the assistance,
I did try fsck (the instructions detailed on apple's site) and ran into that error. It does not seem to be able to repair (since it is the boot disk?) I tried to boot into single-user or into verbose mode, but neither worked -- my computer booted regularly. I tried a safe-boot with shift; that hung my system at the spinning gray apple BIOS screen. I am the only owner of this powerbook, and have never enabled open firmware, so I am a little clueless to why none of these modes work. I'm going to try the PRAM and then booting from media, and doing disk utility.
Thanks
Owen

Whoops, well, it looks okay now

Well, I was stupid about single-user, and forgot to hold down command, upon booting to that and running fsck (only once) everything looked okay, I ran it again for good measure, and then did it in the terminal app one more time once rebooted --- and it says Volume appears all okay.
Thanks for the help, glad that it appears fine now,
I'll keep my eye on it,
Thanks,
Owen