Complete formating HDD with WindowsNT

I have a HDD, which had installed NT-Server 4.0

Now i want to install NT-Workstation on this HDD, because the Server is not needed.

After making new Partition and formating with NT-Workstation-Setup, the Setup is able to find the “boot.ini” and other Datas.

How is it possible to make a new Format without a Possibility to have any old Datas on the HDD?

Great thanks for answers!