ok, I have used less than half of my PC's 1 TB HD so far, I have bought a 1 TB external HD to back up the pc... now I did that, and it says it didn't have space for a system image.... now that doesn't make sense unless the system image is duplicating the backed up files.... (as I only have about 400gig of my PC's HD used) do i just need the system image? will that contain everything I need for my backup?

Thanks!

I suppose it depends on what the software you are using is and whether it is making an image of the actual data or the whole disk and whether or not the resulting image is compressed.

just windows 7 "create a backup" function, which says it backs up files and creates a system image... after some playing I have now succeeded... however i have 197 gig free on the external HD and 485 gig free on the internal HD so it must have duplicated some stuf.... not to worry, at least I know I have everything (my music and pics being the important stuff!) and can restore if ness

You could look into using a third party program. I use FBackup. Very easy to set up. If set to do a mirror backup the first backup takes longer. Evey backup after that runs a lot quicker, basically mirror imaging the source folder that you have chosen to backup. Its free as well.

just windows 7 "create a backup" function, which says it backs up files and creates a system image... after some playing I have now succeeded... however i have 197 gig free on the external HD and 485 gig free on the internal HD so it must have duplicated some stuf.... not to worry, at least I know I have everything (my music and pics being the important stuff!) and can restore if ness

What's happened is that you've done both types of backup. This is both good and bad, for these reasons:

Good: The system image allows you to recover from a total loss right to the point of backup. All your settings, drivers, programs and data files are restored so you can just get a new, blank hard drive and be totally back to the point of the last backup very simply. The normal backup will only cover your data and mean that you'd have reinstall Windows and all your apps manually.

Bad: You can't restore individual files from a system image, it's all-or-nothing. This is why you've also got a "normal" backup that you can browse through and restore just what you need. This is why your available space is much smaller than you expect, because (as you rightly said) you have some data stored twice. Once as part of the system image, and then once as part of a discrete backup set. Each offers a different "selling point" so I'd try and keep both going while you have the space to.