What's happened to the disk capacity?

Last night I took a look at the free space on the disk in my laptop. It looked quite a lot smaller than I expected so I booted up a utility and found that there was a 9.4GB file which shouldn't have been there.

The whole process took less than a minute - booting the utility, logging the disk, finding the file, viewing it and deleting it - but the interesting thing is that I didn't use any XP tools to do it. I don't know them well enough and the whole Windows approach of trying to hide things from the user leaves me vaguely uneasy. I'm sure that those tools would have worked, it's just a matter of confidence. My approach means that I have seen the file and been able to take a quick look at it before deleting it.

It's one of the features of growing older - a reliance on doing what you know works.