Well, I have Windows XP Media Center Edition v 2002 SP2, and I haven't added anything to it. I just would never install anything if it said it did anything to the OS, enhance, speed up, add features, anything. I have learned that the best way for me to keep it running smoothly is to leave it strictly alone. I have a lot of programs on my machine, but so far as I know, the only ones running on NET are pdn, stuff from Microsoft, and three programs I've written myself.
Again, today, I noticed that maximizing the window (pdn) fixed the problem. I'm working on a website and I keep a lot of programs open. Usually I have pdn maximized, but sometimes I have to size it down to make room for something I need to refer to as I'm using it and when I'm done, minimize it without maximizing first. Then, later, when I need it again, and activate it, and click Open--no Open dialog. But if I click Esc, to cancel the Open, maximize the window, then click Open, it works. That's not a very good explanation, but I can't remember what it's called when you click the middle button at the top with two overlapping squares.