Before you answer, this isn't the typical PerceivedType="video" question. I'm not trying to get Media Center to recognise QuickTime or Matroska files or anything like that. I'm asking here because it is Windows XP Media Center Edition 2005 (with SP2) that I'm trying to do this on, and want to make sure that I'm not missing something because of some bizarre undocumented difference between vanilla XP and MCE XP. I'm doing a little tinkering around with the registry trying to reacquaint myself with how Windows deal with filetypes. I used to know a fair bit back in the Windows 95 days, but things have changed a bit since then. Mostly, they've gotten more complicated. I know about the three basic groupings in the [HKEY_CLASSES_ROOT] key (well, three for my purposes). The Extensions (anything beginning with a period), the ProgIDs (anything not), and SystemFileAssociations (among other special ProgIDs, like Folder, File, Directory, *, and one or two others.) It looks like the [HKEY_CLASSES_ROOT\SystemFileAssociations] is pretty much a subtle way for Microsoft to impose their own programs as the defaults for opening certain extensions. Or at the very least adding those damned annoying "Add To Playlist...", "Add To Sync List...", "Add To Burn List..." menus. But they also have a few more special keys there such as [image], [audio], [text], , and a few others. These magic keys correspond to the PerceivedType string value associated with the extensions. The great thing about that is that you can add the appropriate [shell/open.MPC] to the [systemFileAssociations\video] key, and suddenly you have "Open in Media Player Classic" on all of your video files. You can even associate a [DefaultIcon] to it. All this I learned spelunking around MSDN (http://msdn.microsoft.com/library/default...._file_types.asp). (After way to much set-up, I'm getting to my actual question.) What I've done, because I'm as particular as the next nerd about certain things, is give [systemFileAssociations\video] a generic audio/video icon, and marked a bunch of various extensions (.mov, .qt, .rm, .ts, .ogm, .vob, and so on) as PerceivedType="video" and nothing else, with the expectation that they'll show my generic audio/video icon, and I'll also be able to right-click and choose "Play in MPC", or "Play in VLC". I've also created an [.mpeg1] extension and given it all the same properties as the pre-built [.mpg, .mpe, .mpeg, etc]. (And finally, here's the problem/question) The pre-built [.mpg, .mpe, .mpeg] extensions/progids all work exactly as advertised. They show the icon properly, and the right-click context menus, all pulled right from the [systemFileAssociations\video] key. Great. But the [.mpeg1, .mov, .qt, .vob] extensions that I created from scratch only show the icon. They're not pulling the right-click context menus correctly. So obviously my assumption is that I'm missing something. Some vital, nearly insignificant-looking, reference that says "Yes, these really are PerceivedType="video" files." Does anybody have any ideas? Anybody with some more knowledge on the subject of Windows File Associations, and Perceived Types than myself, and seemingly MSDN? For what it's worth, this is a clean install, and I have zero problems with reinstalling for as many times as it takes to get this right. It's not my main machine anyway.