NS_E_CHANGING_PROXY_EXCEPTIONLIST (0XC00D10C2) Fix: Proxy Exception List Locked

The proxy exception list won't let you edit, and Windows Media Player throws 0XC00D10C2 — yeah, that's annoying. Here's the fix.

Quick Fix: Switch Proxy Mode to Custom First

1. Press Win + R, type inetcpl.cpl, hit Enter. That opens Internet Properties.
2. Go to the Connections tab, click LAN settings.
3. Under Proxy server, check Use a proxy server for your LAN — but don't fill in an address yet. Just tick the box.
4. Then check Bypass proxy server for local addresses — that's the exception list equivalent.
5. Click OK on both dialogs to apply.
6. Now open Windows Media Player, go to Tools > Options > Network.
7. Under Streaming proxy settings, find the protocol (usually HTTP). Click Settings.
8. Select Use proxy settings of the Web browser, then click OK.
9. Go back into that protocol's settings again — now pick Custom. The exception list field will be editable.

That's it. The error won't reappear. The exception list is now yours to edit.

Why This Works

What's actually happening here is that Windows Media Player talks to a system proxy configuration provider — either Internet Options or Group Policy. The error NS_E_CHANGING_PROXY_EXCEPTIONLIST (0XC00D10C2) means the proxy mode is set to Browser or System, both of which lock the exception list because they inherit settings from the OS-level proxy. The exception list is a property of a custom proxy configuration — not a global one. By first enabling a proxy server in Internet Options (even a dummy one), you force the system to expose the exception list field. Then switching Windows Media Player to Custom directly hands control of that list to the app.

The reason step 3 works is that any proxy server enabled at the OS level creates a bypass list container. Without a proxy server defined, the exception list doesn't exist in the configuration tree — so Windows Media Player can't edit it.

Less Common Variations

• Group Policy locks it down. If you're on a corporate machine, gpedit.msc under Computer Configuration > Administrative Templates > Windows Components > Windows Media Player > Network may have Streaming proxy settings set to Disabled. You can't override this without IT admin rights. The error won't go away until the policy is relaxed or removed.
• Registry corruption. Rare, but happens if HKEY_CURRENT_USER\Software\Microsoft\MediaPlayer\Preferences\Proxy gets mangled. Export it, delete the key, restart Windows Media Player, and reconfigure from scratch.
• Different Windows versions. On Windows 7, this error is more frequent because Windows Media Player's network panel is more sensitive to missing registry entries. On Windows 10/11, the GUI is stricter about showing the exception list field — you can get stuck even after fixing the proxy.
• Third-party VPN or proxy software. Apps like Proxifier or PuTTY's SSH tunneling can inject dummy proxy entries. Disconnect the VPN or kill the proxy app, then redo the steps above.

Prevention

Once you've got the exception list working, don't toggle the proxy mode casually. If you switch Windows Media Player back to Browser or System, the exception list reset. To avoid hitting this again, set your proxy mode to Custom permanently, even if you don't need a proxy — just leave the address and port blank. The exception list stays editable and the error won't come back.

Also, before messing with proxy settings elsewhere (like in an app or Group Policy), always check whether Windows Media Player is reading from a system-level proxy or its own config. If the system proxy is disabled, you'll get 0XC00D10C2 the moment you try to edit the exception list.

Bottom line: you can't edit what doesn't exist. The system proxy bypass list only appears once a proxy server is enabled at the OS level. Work around that, and the error vanishes.