Modrewrite and duplicate content issues

what should I do with the old pages?

[Zygoot]

A long time ago I used modrewrite to rewrite quite a lot of pages from oldurl.php?v=x to newurl/x. But I forgot to block the old filenames and they are now still indexed by search engines.

So SEs have indexed two identical pages. Is it possible that some of these pages have received a duplicate content filter because of this?

And how should I prevent the old file from getting indexed, is a disallow command in robots.txt enough?