As porter points out, reformatting won't help. The SCSI ID is not a variable that is stored on the drive. Reformatting may be necessary for other reasons, but resetting the ID isn't one of them.

Look for some other problem, such as the one Wally identified. Carefully check how you hooked up the ID-setting cable. There's one right way, and several wrong ways to do it. If you didn't pay attention to how it was connected originally, and randomly hooked them back up without regard to orientation, then you should expect trouble. Just fyi, one pin of each pair of pins is connected to ground, so one entire triple will be grounded. The other three pins are then selectively grounded (or not) by the ID switches. That should be enough information so that, with the aid of a multimeter, you can hook it up right.