I've had a quick look at the Acronis True Image WD Edition user manual which can be downloaded
here.
Looks simple enough to follow and will pretty much guide you through the cloning procedure (see chapter 10). Can be done using an external USB enclosure. Just be aware that the particular version of Acronis TI that this is based on is reported as having issues under Windows 7 but should be ok for XP or Vista.
Good luck with it.