I sincerely hope that that is a USB2 connection, otherwise it’s going to be a very slow backup!
One question that has to be asked is, what is the purpose of this backup? If it is to safeguard your data, then you don’t need to back up the whole drive, just the data portions of it. If on the other hand, you are planning to make some major changes to the laptop and want a way to recover then that is an entirely different ball game.
For regular data backups, you could simply set up the folder synchronization that XP has built in and let that take care of it - each time it is connected it will copy over any files that have changed to the backup drive. It also means that the files on the backup drive are readable from another machine without using any special software.
For full backups, you can go with a commercial product, or simply use windows backup. Both have the ability to backup, verify and restore, the backup is stored in a single archive file on the remote drive, which means the corresponding software is needed to access it from any other machine.
For the ultimate backup (everything on the disk including the boot partition), go with a drive imaging software such as Symantec Ghost or one of its competitors. This will create an image of the disk which, when written back, will put everything back as it was.
The thing I like about my Maxtor+ is that in addition to backing up files, it has a section called “Lifeboat” which backs up the OS. When reinstalling, it means all my Windows Updates are restored to my hard drive so there aren’t hours spent re-downloading.