I was at my fathers house yesterday, his PC had what may be a bug.

My father has been a programmer since the late 70's, and no one is allowed to use his machine, but me (programmer since the late 80's). I mention this to you so you know this is unlikely to be user related.

He had a file named '~' in the C:\ directory. The file is a binary file, that when hexed had what looked something like his address book.

Is this familiar to any of you security folks?

I hope I put this in the right forum.