Insert a diskette in the A: drive (where A: is your floppy drive).
1) Open "My Computer", right click the A: drive and select "Format".
2) Open the Windows Explorer, right click the A: drive and select "Format".
The "Format" dialog box will open. Make sure the options (Capacity, Format Type and Other Options) are correct, then click the "Start" button.
Remember that formatting a disk removes all information from the disk.
You cannot format a disk if there are files open on that disk. If the disk has been compressed, use DriveSpace, or other compression software, to format the disk.