Media center keeps recording the same movies

I have a small problem that is growing into a larger one. I have Windows vista premium and when I use media center to record a movie it works fine. Then, to save space I record it to a DVD and then delete it. The problem is that the next time it's on it gets recorded again. It's getting to be a real problem now though because the list keeps getting bigger, and it's filling up my hard drive.
How do I clear the memory in media center so it stops searching for these same movies?
Thanks