Quote:
does emplode mark those spots as bad so it doesn't write to the again?


Yes and no. This error handling is dealt with at the disk itself. When you read from a bad block, you get an error (after a number of retries). When you write to the disk, if there's an error, the drive will remap that block to somewhere else.

So, reads: no; writes: yes, within reason. Within reason, because there's only a small number of spare blocks on the disk for this purpose.

If you want to ensure that bad blocks are marked as such on the disk, you'll need to plug it in as the second disk, with a known-good first disk. Then, using the developer image, issue the command:

dd if=/dev/zero of=/dev/hdc

...which will write zeros all over the second disk. Any sectors that cannot be written to will be remapped somewhere else. Obviously, you'll need to run the disk builder (see the FAQ), since the disk is now filled with zeroes.

OTOH, if the disk is that bad, just buy another one. 20Gb and 30Gb disks are relatively cheap and easy to get hold of.
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-- roger