I have to agree Ed Botts "Why I don’t use registry cleaners". I should preempt that with; I don't use any third party Registry cleaners. I used to use Microsoft’s, before they stopped offering it.
I would urge people to NOT "optimize" their registries. I have yet to see any significant results from any cleaning/optimization I have ever done. I have however had very bad things happen after running some of these programs. I would avoid them at all costs.