Not always. Sometimes a format just resets the disk structure and scans for
obvious errors without actually overwriting and testing every sector.

I've faced this problem as well. I qued some videos the other night and later watched them to find that some were KP. I deleted them. Then I previewed some of those still in que and deleted some more that were iffy.

I thought I was good, then I realized about a week later that I forgot to delete the file fragments or whatever. However, I don't even share my files, nor do I share file fragments, so do I have anything to worry about?

I also didn't know that a regular delete wasn't secure. So I guess my HD still has fragments on it. This sucks. I think I'm fixing to uninstall limewire. Too much trouble.