The "best" one is the one that works when you go to do the restore. There are several good imaging backup programs. The fly in the ointment is if you have an unusual disk controller, when you boot the Restore CD to lay the image back on, it may not recognize the HD. Before even doing the backup, make the Restore CD and see if you can boot it and go into the restore program without errors. If you can see your HD then do the backup. Esp. if you have to burn to DVD this will save a lot of wasted discs since each backup program uses its own format.
It's easier if you have an external USB drive to store the backup image. The free Macrium Reflect program is a nice backup. There are other free ones available also. None of it does you any good if you can't restore when the PC won't boot from the HD(disaster recovery.) Just make sure the Restore CD supports your hardware, then choose from the ones that do.
You can find some profiled on Gizmo's site: Gizmo's Freeware Reviews
also try: thefreecountry.com: Free Programmers' Resources, Free Webmasters' Resources, Free Security Resources
I'm sure there are a few in the Free Software List on this forum too.