NS_E_WMPCORE_CODEC_NOT_FOUND (0XC00D109B) — WMP won't play a file
Windows Media Player can't play a file because it's missing the right codec. This fix gets you playing again in under 30 seconds with a free codec pack.
30-Second Fix: Install the K-Lite Codec Pack (Basic)
This is the fix I use on every single machine that throws this error. I've been doing this for years, and it works 99% of the time.
- Open your web browser — Chrome, Edge, or Firefox, doesn't matter.
- Go to the K-Lite Codec Pack download page at codecguide.com/download_kl.htm.
- Click the 'Download Basic' button — you'll see three options: Basic, Standard, Full. For this error, Basic is all you need. Standard adds a media player you won't use, Full adds encoding tools you don't need.
- Wait for the download to finish — it's about 15 MB, so it takes maybe 30 seconds on a decent connection.
- Double-click the downloaded file — it's named something like
K-Lite_Codec_Pack_1800_Basic.exe. - Click 'Next' through the installer — don't change anything. The defaults are fine. When you see the 'Select Components' screen, just leave it as-is.
- Click 'Install' — you'll see a progress bar. After it finishes, you'll see a screen that says 'Installation Complete'.
- Click 'Close' on the installer.
- Try playing your file again in Windows Media Player — double-click the file or drag it into WMP. It should play immediately.
If it still doesn't play, close WMP completely and open it fresh. Sometimes it needs a clean start to recognize the new codecs.
That's it. You're done in under a minute. If this didn't work for you, move to the next step.
5-Minute Fix: Check for a Corrupted File or Wrong Format
Sometimes the codec isn't the problem — the file itself is. Here's how to check.
Step 1: Try a different media player
Download VLC Media Player from videolan.org. VLC has its own built-in codecs and doesn't rely on what's installed on your system. If VLC plays the file fine, the problem is definitely a missing or broken codec in WMP. Go back to the 30-second fix and make sure you installed the Basic pack. If VLC also can't play it, the file is probably corrupted or in a format that's not widely supported.
Step 2: Check the file extension
Right-click the file and select Properties. Look at the 'Type of file' field. Common codec-needy extensions include:
.mkv— Matroska video, needs a codec pack in WMP but plays natively in VLC.flv— Flash video, same story.webm— WebM format, not natively supported in WMP.mp4— Should play fine in WMP unless the encoding is weird
If the file is .mkv or .flv, the K-Lite Basic pack covers those. But if you have an older version of K-Lite (pre-2020), it might not. Update to the latest version.
Step 3: Try a second file of the same type
If you have another file with the same extension (like another .mkv), try that one. If it plays, the first file is corrupted. If it also fails, you're still missing a codec.
If you're still stuck after this, move to the advanced fix.
15+ Minute Fix: Repair Windows Media Player or Reinstall Codecs
This is the nuclear option — but sometimes you need it. Do these steps in order.
Step 1: Uninstall the existing codec pack
Open Control Panel (press the Windows key, type 'Control Panel', hit Enter). Go to Programs and Features. Find 'K-Lite Codec Pack' in the list, right-click it, and select Uninstall. Follow the prompts to remove it completely.
After it's gone, restart your computer. Don't skip this restart — it clears out any stale codec registrations.
Step 2: Reinstall K-Lite Codec Pack (Full version this time)
Go back to codecguide.com and download the Full version this time. The Basic pack covers most files, but the Full version includes extra codecs for less common formats like QuickTime and RealMedia. Install it with the default settings again.
After installation, restart your computer one more time.
Step 3: Repair Windows Media Player
If the codec pack didn't help, WMP itself might be broken. Here's how to fix that.
Open Settings (Windows key + I). Go to Apps > Apps & features. Scroll down to Windows Media Player. Click it, then click Advanced options. Click Repair. Wait for it to finish — takes about a minute.
If that doesn't work, go back to the same spot and click Reset. This removes all your WMP settings and library data, but it fixes deeper corruption.
Step 4: Enable Windows Media Player features (Windows 10/11 only)
Sometimes WMP gets disabled by a Windows update. Open Control Panel > Programs > Turn Windows features on or off. Scroll down to Media Features. Expand it and make sure Windows Media Player is checked. If it isn't, check it, click OK, and restart.
If it's already checked but grayed out, that's normal — it means WMP is installed. You can try unchecking it, clicking OK to remove it, restarting, then checking it again to reinstall it fresh.
Step 5: Last resort — use a different player
If none of this works, accept that Windows Media Player is a dead end for that file. I recommend VLC or MPC-HC (Media Player Classic — Home Cinema, which comes with the Full K-Lite pack). They're both free, both handle almost everything. You won't get this error again.
That covers every path. Start with the 30-second fix, and you'll probably be done before you finish reading this sentence. If not, work your way down. You'll get there.
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