There is no low level format on IDE/ATA drives.
What those PC "Low Level Format" tools do, is to write the whole disk full of 0 or 1, starting from the first physical block and ending at the last physical block (on amiga terms, this will overwrite RDB, all partitioning information, all partitions and user data).
HDToolBox "Low Level Format" does not do this. It send a special SCSI command to the device, and this is always ignored or reported as an error by IDE/ATA drives.
IDE/ATA drives can be reinitialized though, as described above. If this "so called" low level formatting (which really is not low level formatting at all) is performed, it will take VERY long time. How long? Depends on the size of the HD and the speed of the IDE bus. To get rough idea, divide the total size of the HD (MB) with the speed of the interface (MB/sec), result is seconds. Depending on the tool (if it does verify), the time could double. Also allow some percentage of overhead.