Unmounting filesystem for fsck

I need to repair the filesystem on my Linux partition in order to resize it with Partition Magic 8. fsck sometimes runs automatically, on startup, when my filesystem is too bad, but I cannot seem to run it manually. I've tried unmounting my filesystem in the single user run-level, but I get the following error message:
sh-2.05b# umount /dev/hda2
umount: /: device is busy

The partition for my boot directory, /dev/hda1 unmounted fine.

I did go through all run-levels, to Gnome, and then typed 'telinit 1' in an xterm.

I have two questions:
How can I make '/' unbusy, so I can unmount it?
and
Are there other programs that repair linux filesystems and where can you get them?

Repairing a live fs is a dangerous thing! Don't do it!

Use fuser -v /dev/hdxy to check which app is using that file. However, since you're trying to check the root fs this is a bit tricky because that's where e2fsck is so it automatically tags that hard drive has busy. You could try to force e2fsck to read the fs in read-only mode and if any error gets spitted out just go through all the hassle of booting off a floppy (or use tune2fs to mark as dirty and reboot).

You need to boot to runlevel 1 and not change to runlevel one from an xterm, that won't work. Whenever you boot type linux 1 or whatever your kerenl name is from GRUB/LILO. This will automatically boot to runlevel 1 so you can unmount the root filesystem and fschk it.