I have a strange line in my fstab file:

none /mnt/hd supermount dev=/dev/ide/host0/bus0/target1/lun0/part1,fs=ext2:vfat,--,umask=0,iocharset=iso8859-1,kudzu,codepage=850 0 0

When mounted, the /mnt/hd directory is empty.
If I unmount /mnt/hd and delete this line in fstab, it reappears when I restart my computer.

What does this line mean? How can I delete it permanently?

If it can help, here are some details:
- I have 2 hard disks: hda (3 partitions: root, swap and home) and hdb (1 ntfs partition)
- I run Mandrake 10.0

It's happening because of the ntfs partition. I believe your system is trying to configure it as a windows partition of some sort.

Indeed, this happens since I installed the second hard disk (it is ntfs because it comes from a windows machine and it contains some data important to me).

Anyway, is there a way to prevent the system from trying to configure it automatically (except of course formatting the disk in ext2)?

A quick Internet search for "linux supermount" lead me to http://supermount-ng.sourceforge.net/ but basically it tells supermount to take control of /mnt/hd and uses supermount specific coding to mount your windows partition. If the directory is empty then it's probably something supermount didn't guess right at, like the filesystem type (fs=ext2;vfat?) that causes it to fail. Since I know nothing about how supermount works and don't currently have Mandrake installed anywhere I would suggest looking at the web site above and at the installed documentation (man supermount, info supermount, supermount --help) to get it to either correctly mount your windows partition or not try.