If you have a 96GB empeg with only 10GB full then you'll need 96GB of space to back it up rather than 10GB.

Ghost images can be compressed, and also set to not copy empty space. I use Ghost on my PCTV machine, so that I can quickly get back to an OS load to watch TV if the current one breaks. The image ended up compressing pretty well, and with a single dos boot disk, I can pull it back over the network.

There is a opensourced program that does what Ghost does, it may be worth a look for those wanting to dump a non-playable backup to their computers. It's called Partition Image.