If you drive a copy of a file down to one copy then there is no backup. Two copies is barely a backup since one loss and you fall into a state of no backup.
This is all very old IT rules and lore but worth going over again and again until we feel like it's good enough. Many folk have no backup at all.
There are dozens of backup softwares out there. I continue to use Syncback and Goodsync. Now a little use of Dropbox as well.
Bob
Laptop: Windows 7 Pro
Desktop: Windows 7 Pro -External HD
I currently have all my files on my laptop being backed up over the network to an External HD. I would like to purchase a portable HD to put older files that i'm not currently using onto. So on my internal HD I would have my important everyday files. I would like to have my internal HD and the portable HD backed up automatically to the External HD. Any suggestions?

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic