Backup/Reinstalling

I have never backed up my PC operating on Windows XP Home
Edition (after owning it for 18 months)and am getting
nervous should I catch a virus that would cause my PC to
crash and I end up losing everything on it.

I have referred to Windows XP Magazine and numerous
websites and they all claim I should have an installation
CD and can install a back up facility/operating software
from there.

However, my PC came with Windows XP Home Edition pre-
installed and I cannot obtain a copy of the Operating
Software to install the back up facility.

Similarly, I have no way of reinstalling Windows XP Home
Edition should I need to.

Please can someone let me know how I can

1) Obtain a copy of a Windows XP Home Edition CD

2) Create a back up of my PC so that I can reinstall the
OS in the event of a system crash/virus

Look forward to hearing from you soon