Backing up multiple laptops to one Ultra external drive

I have 3 computers operating on Windows (XP, 7 & 8) which I want to backup to this external drive.
Can I create new different directories on the external drive which would be associated to each computer and backup to that directory or do I have to partition the external drive to 3 parts to be able to handle the backup?

Hello,

The Passport Ultra comes with WD Smartware backup software. This software is capable of backing up multiple computers and you don’t have to create different directories or partitions. The software will label each backup after each computers name.