Opening the can of worms
You're trying to stream from a network share or a media server, and Windows Media Player just gives you that ugly 0XC00D0029 error. Yeah, it's frustrating. Let's skip the diagnostics and go straight to what fixes this most of the time.
The fix: kill the proxy override
What's actually happening here is that Windows Media Player, specifically version 12 on Windows 10 and 11, tries to use the system's proxy settings even for LAN traffic. That makes zero sense for a local stream, but that's what it does. The fix is to tell WMP to bypass the proxy for local addresses.
- Open Windows Media Player.
- Press Alt to show the menu bar if it's hidden.
- Click Tools → Options.
- Go to the Network tab.
- Under Streaming proxy settings, select HTTP and click Configure.
- Choose Autodetect proxy settings (not Use proxy settings).
- Repeat for MMS and RTSP protocols.
- Click OK all the way out and restart WMP.
This forces WMP to detect the network directly instead of routing through a proxy that may not exist or is misconfigured. The reason step 6 works is that 'Use proxy settings' tells WMP to respect Internet Explorer's proxy configuration — which on many corporate or home networks is set to something that chokes on local multicast or unicast streams. Autodetect lets WMP negotiate the connection itself.
Why this fix works
The error code NS_E_CONNECTION_FAILURE (0XC00D0029) is thrown when WMP's network stack can't establish a TCP or UDP connection to the source. On a local network, the most common cause isn't a dead server — it's WMP trying to use a proxy that either doesn't exist or doesn't support the streaming protocol. When you switch to autodetect, WMP sends a direct HTTP request to the IP/port of the media source. If the server is alive and the port is open, the stream starts within seconds.
I've seen this on Windows 10 21H2 and Windows 11 22H2 with media servers like Plex, TVersity, and even plain SMB shares. The proxy setting gets inherited from the system's old Internet Explorer configuration, which you might have set years ago and forgotten about.
Less common variations
Firewall blocking the stream
If the proxy fix doesn't work, Windows Defender Firewall might be the culprit. WMP uses ports 1024–5000 dynamically for streaming, and some security software blocks that range. Here's the quick test: temporarily disable Windows Defender Firewall (don't leave it off) and try the stream again. If it works, add an inbound rule for C:\Program Files\Windows Media Player\wmplayer.exe on both TCP and UDP.
IPv6 vs IPv4 mismatch
Some home networks have IPv6 enabled but the media server only speaks IPv4. WMP can get confused and try IPv6 first, timeout, and throw 0XC00D0029. You can force IPv4 by disabling IPv6 on the network adapter for testing: Control Panel → Network and Sharing Center → Change adapter settings → right-click your adapter → Properties → uncheck Internet Protocol Version 6 (TCP/IPv6). If the stream plays, leave IPv6 off or configure your media server to handle both.
Corrupted WMP library
Rare, but I've seen it. A corrupted media library can make WMP hang when trying to access network resources. Reset it: close WMP, open Run (Win+R), type %LOCALAPPDATA%\Microsoft\Media Player, delete everything in that folder, then restart WMP. It rebuilds the library from scratch.
Prevention
Once you've got the stream working, lock it down:
- Set WMP's proxy to autodetect for all three protocols (HTTP, MMS, RTSP) and never touch it again.
- Keep Windows Defender Firewall on, but add the explicit exception for wmplayer.exe.
- If you're on a corporate network with a real proxy, you'll need to talk to IT — but the autodetect setting usually works with most enterprise proxies that support WPAD.
The worst thing you can do is disable the firewall entirely. Buy a cheap router instead if you're desperate — a Netgear or TP-Link with UPnP enabled will handle local streaming without any WMP config hassle.