How to Re-Format an WD Passport 160G portable hard drive

Back in Sep’07 I purchased a 160G Passport only to find it was format in FAT32, not NTFS as is my Dell Inspiron E1505 notebook.    I tried to use it as a back-up drive, but cannot get the Windows Back-up function to complete it’s work.   Always get the error that the drive must be formatted as FAT32.  My PC has only 40G, so the 160G Passport should be more than adequate.  So, how can I re-format it to work with my PC to backup to?