If the drive is the bootable drive:
Backup all data (on all of the hard drives in the computer).
Reboot to the installation CD for the operating system (Windows).
Select the option to reformat the hard drive.
Follow the procedure to reformat the hard drive and reinstall Windows.
If the drive is a storage (secondary) drive:
Backup all data on the drive whose partition will be changed.
Right-click on My Computer.
Select Disk Management from the left column.
In the right column and bottom window, find the hard drive (labeled, for example, Disk 1).
Locate the partition just to the right of the Disk 1 box.
Right-click on the partition.
Select Delete Partition.
Wait until the partition becomes Unallocated Space.
Right-click on the Unallocated Space.
Select New Partition.
Follow the Create Partition Wizard to create an NTFS partition.
To convert a volume to NTFS from the command prompt
See Microsoft document 307881 for instructions.