Reducing hardware acceleration is the primary method of addressing the green screen issue. If that does not work, you can update your codecs, re-register your player with Microsoft or try to install the latest drivers for your display adapter.
Reduce Hardware Acceleration
When your hardware is accelerated, your video card is configured to process a video faster than your player software can display it. This can cause the green screen in Windows Media player. To fix this, reconfigure your hardware acceleration through the Control Panel.
In Windows 7, click the start button and click Control Panel.
Under the Control Panel's Appearance and Personalization, click Adjust screen resolution.
Click Advanced Settings.
Select the Troubleshoot tab and click Change settings. Move the Hardware acceleration slider toward None or turn off hardware acceleration completely.
If the Change Settings button is grayed out, as shown, you are not able to adjust the hardware acceleration. Use an alternative solution described in this article.
In Windows 8, type Control Panel in the search bar and click Control Panel from the results that appear.
As with Windows 7, click Adjust Screen Resolution under Appearance and Personalization. Click Advanced Settings and slide the Hardware acceleration slider to None.
Update Your Codecs
Codecs compress or decompress your media files. There are hundreds of codecs in use today, and your computer may not have all of them. Windows Media Player uses these codecs. A green screen is a sign you need to update your codecs. Windows automatically updates the codecs created by Microsoft with regular updates. If you are using software not created by Microsoft, you can download the codecs from the software manufacturer.
Using codecs not created by Microsoft could cause playback issues or introduce viruses and malware into your system. Microsoft warns against trusting downloads of free codec packs that cover a wide variety of codecs. Only download from trusted sources.
To manually download codecs to solve a green screen issue after the automatic update process has failed, go to Microsoft for the Codec Installation Package.
Click Open or click Save File and double-click the file when the download is complete. This will install the latest codecs on your machine. Test your player to see if the issue is resolved. If not, try to re-register your player.
Re-Register Windows Media Player
You can re-register the Media Player file to help resolve player issues that were not resolved with hardware acceleration configuration and codec updating. Open the command prompt by clicking Start, type cmd and press Enter in Windows 7. In Windows 8, type Command Prompt in the search field and click Command Prompt from the list.
At the prompt, type regsvr32 wmvdecod.dll and press Enter. You will receive a window if this succeeds. If this fails, update your Media Player. You can test success or failure by trying your player again. Contact Microsoft for support if this fails.
Install the Latest Drivers for Your Display Adapter
Open the Control Panel, click System and then click Device Manager.
Expand the Display Adapter section, double-click your display adapter from the list, click the Driver tab and click Update Driver.
Click Search automatically for updated driver software.
If these solutions fail to resolve your issue, Microsoft and the Microsoft community offer support in the form of finding the answer in Microsoft's wide array of self-support options, asking the community to get expert help from other users or getting technical help from Microsoft. The last option is normally a paid service but may be free if you have a warranty.