The simplest way to do it is with ASR (automated system recovery). You have to go to drive properties, then backup, then choose ASR. You'll do a regular backup but it will ask you to create a special diskette in the process. Once you have backed up to your second HD, you can restore your system to its backed up state by booting with the WinXP Setup CD, and choosing ASR when you're prompted. You'll need that diskette you made earlier. What will follow is that Setup will format the drive you backed up onto your second HD, it will install a bit of XP (about 5 minutes worth), and then restore your drive from the backup. During the whole process you don't have to lift a finger once you've put in the floppy disk.
Hope this helps,
Redshadow