FDISK does not low level format the hard drive. That is a Hi level format utility and there is a big difference between them! Why reinvent the wheel with a debug routine? Go to this Seagate site and download the utility called Disk Wizard. http://www.seagate.com/support/disc/drivers/discwiz.html
The download routine for Disk Manager creates a bootable diskette. Boot from the diskette to start Disk Manager. After startup, Select Advanced Options | Maintenance | Options | Utilities. Select thedrive you want to erase, then select Zero Fill or Low Level.
Note: The Zero Fill option runs more quickly and removes data just as thoroughly as the Low Level option.
Be sure to read the page carefully and download the right version for your OS.