As I remember it, writing zero's to the drive writes them to the entire drive. Unless the software has changed and can now write very specific parts. I would be careful with that. Whilst what allformats suspects is feasible, the boot sector, which is the first 512KB loaded at startup of the O/S can be damaged or corrupted, you dont wanna chance screwing up other areas of the HDD.
Is there anything important you chance losing from data that you can't just do a full format, and set up partitions from scratch.
Check your PM.