1. It is possible to create 2 partitions on your new HDD
2. To format them in NTFS you're going to need to format them from a Windows PC or when you are booted under Windows in Bootcamp as Disk Utility in OSX can't format NTFS.
I assume the external HDD is USB2.
Use BootCamp to boot into Windows.
Plug in the USB2 HDD
This article explains how to partition and format an external HDD using the windows XP tools
Can XP format my new USB external hard drive? - XP Maximized
I also have found an article where it is explained how to use BootCamp to boot XP from an external HDD
HOWTO: Booting XP from an external USB hard drive - OnMac.net Forums