True Image Home - 2009: Hard drive space being consumed with "Other Files"

When I go into the "Protection State" section of the s-ware, I see that 210.7 GBs of my 521.5 GB ext. hard drive is consumed by "Other Files" in red, while my backup has only consumed the expected 28.59 GBs. I don't have a clue what these "Other Files" are.
How do I get a picture of what files have been written to my external hard drive and if there are unnecessary ones, how do I delete them and stop them from being written there again?

Thx;

Steve P.