Huh???
What is the /s switch supposed to do? What file system is your drive?
If you are trying to install Windows 2000 you get the option to partition/format the drive during the install process.
If you already have Windows 2000 installed and just want to format another drive use the Disk Management tool to format the drive. Go to Start->Settings->Control Panel->Administritive Tools->Computer Management->Disk Management.