Is it still important for me to do back-up's?
You've answerd your own question really, when you said "I can't think of anything I would want to retrieve from it if it crashed/was stolen etc."
If you're sure about that, particularly with regard to emails (and email addresses) then no, there's no need for a backup. Windows will make automatic backups of your computer's registry settings at regular intervals, so you could restore one of those if you hit problems. It won't backup emails or any other form of data files however, and if you install any new software it will disappear if you use a restore point that was prior to the installation date.
If you have the original Windows installation disk, and the installation disks for any software you've installed you would be able to get the computer up and running again if the worst happened. If you don't have the to think about making a disk image, so you could restore the computer to its present state.
Does that help?