This thread delivers!
Just as a reference, I scanned my registry for orphans, to see how many I had.
My computer is being used daily, both for work, and for gaming and surfing. I have installed and uninstalled at least a dozen games since I reinstalled the last time, not to mention the myriad of game demos, and a few productivity apps that have been going in and out like male reproduction organs in the feeding apparatus of a very busy woman of eastern European origin.
There was 436 orphaned registry keys.
436 keys in the 8½ months that have passed since I last reinstalled.
This will undoubtly slow my system down to a crawl.
Oh, by the way, the reason some distributions of Ubuntu don't play DVD's, and some other media, out of the box is because the open source players violate patent/copyright laws in some countries. Thus, this funtionality is provided as add-ons, to make sure that the distribution is legal regardless of where it is being installed.
