Formatting is not the same as zero-filling. Formatting just removes the files from the file table. Zero-filing overwrites the sectors multiple times to get rid of the data.
I think both formatting and zer-filling utilities skip bad sectors.
TheMajorMMX - Intel P200 MMX @ 225Mhz - V-Tech (PcPartner) Baby-AT mb w/ Intel Triton TX chipset - Nvidia Riva TNT2 M64 w/ 16MB - 256MB M-Tec SDRAM - Still running.....