marking duplicates for deletion

[Rhod]

Hi - I've brought all my images together at last but now I have quite a few duplicates. I started going through them, manually marking every other one for deletion but then I thought, surely there must be an easier way? So I was wondering if anyone more technical than me (not difficult!) has written a script that can mark every other image for deletion. I know this could be quite dangerous but I would be happy to scroll through and review before deleting, it's just the marking that takes an age.

Many thanks
Rhod