There is a reasonably simple way of copywritng your own material.

1: Put the offending material onto a CD, DAT, or some other sort of tape.
2: Go to the Post Office.
3: Seal it and send it to yourself, or even better, your lawyer, by Registered Post.
4: Go home and wait.
5: When the mail arrives at your place or your lawyer's, DON'T OPEN IT. Never open it unless you have to prove something in a courtroom - and dont forget to get a receipt when you send it.

The legal eagles among you can figure out the implications of doing that; how much legal water it would hold etc, and it is true that I have never put the practise to the test myself.
But I am reliably informed (I hope) that signatures, dates, and receipt numbers take a lot of beating, especially if the case is about who wrote what, and when.

All the Georgie,
Bren.