Here is a Linux command that I am always trying to remember. It checks to see which applications/services are using/keeping busy a given file system. Its particularly useful when you want to find out why you cannot unmount a given file system. If, for example, you want to check and see why you cannot unmount your USB pen drive from /mnt/usb you would type:
/usr/sbin/lsof +D /mnt/usb
It seems that with Fedora 2 suddenly it became hard to umount drives. No bother – just umount -l (l is for lazy) and it will unmount when the activity is finished, usually pretty much right away.