Fix NS_S_WMPCORE_MEDIA_CHILD_PLAYLIST_OPEN_PENDING

This error shows up in Windows Media Player when a playlist or media file won't open because a child playlist is stuck loading. It's a glitch in how WMP handles nested playlists.

So you're trying to open a playlist in Windows Media Player on Windows 10 or 11, and instead of your music starting, you get the error NS_S_WMPCORE_MEDIA_CHILD_PLAYLIST_OPEN_PENDING (0X000D1109). It's that moment when you double-click a .wpl or .m3u file—or even a single track inside a nested folder—and WMP just sits there, no sound, no progress bar. I've seen this most often after importing a huge library from an old Win7 machine, or when someone saves playlists from online radio stations as .asx files. The error code is a warning, not a full failure, but it still locks things up.

What's actually going on?

This error means Windows Media Player's playlist engine is waiting for a sub-playlist—a child playlist—to finish opening before it can play the main media. Think of it like a tree: you click a playlist that points to another playlist (or a media file that contains a playlist reference). WMP opens the parent, but the child hasn't loaded yet. This happens because WMP, especially version 12 on Windows 10/11, is old software that doesn't handle nested playlist references well. It's not a corrupt file; it's a timeout or a race condition where WMP's async playlist loader gets stuck.

The real trigger? Usually a playlist file that references another playlist file relative to its own location, and that path is broken or slow to resolve—like a network share that's sleeping, or a removed USB drive.

How to fix it

You don't need to reinstall Windows or hunt for DLL files. The fix is straightforward: clear WMP's library cache so it rebuilds the playlist database from scratch. This kills any stuck pending states.

Close Windows Media Player completely. Check Task Manager (Ctrl+Shift+Esc) to make sure no wmplayer.exe process is running. WMP can hide in the background.
Open the library cache folder. Hit Windows+R, type %LOCALAPPDATA%\Microsoft\Media Player, and press Enter. This folder holds all the .wmdb database files and playlist metadata.
Delete the contents of this folder. Select everything inside (Ctrl+A) and delete it. Don't worry—Windows will recreate these files when you restart WMP. You won't lose your actual music files, just the library database.
Restart Windows Media Player. It'll show a blank library at first. That's normal. Wait for it to finish scanning your monitored folders (usually Music and Videos by default). This can take a minute if you have thousands of files.
Try opening your playlist again. The error should be gone. If the playlist still fails, the file itself might be broken—check it with Notepad to see if it references a child playlist that no longer exists.

If it still doesn't work

Some playlists are just too old or nested for modern WMP. I've had luck converting .wpl playlists to plain .m3u format using a tool like Playlist Creator. Open the .wpl in Notepad, look for lines like <media src="..."/>, and copy those paths into a new .m3u file. WMP handles flat text playlists better than its own XML-based ones.

Also check if your music files are on a network drive or external disk. If the drive letter changed, WMP's child playlist reference points to nowhere. Remap the drive to the old letter, or edit the playlist paths manually.

And if all else fails? Use a modern player. VLC or MusicBee will open those same files without a hiccup. Sometimes the old software isn't worth the fight.