A reader wrote to us complaining that she couldn't get video files to play in Windows Media Player. Our Helproom expert diagnosed a missing codec, and set about solving the problem.

QUESTION I transferred some Mpeg4 video from a Kodak camcorder to my PC. An orange Play icon appears next to each clip in Windows Media Player, but it refuses to accept them. What am I doing wrong? Karel S

HELPROOM ANSWER This problem usually arises because Windows is missing a codec. This is a small program that functions in much the same way as the drivers for your peripherals; rather than telling Windows how to communicate with hardware, it tells the operating system how to decode (and sometimes encode) the audio and video contained within a file.

If you still have the box for your camcorder, you'll probably find a disc inside that contains the necessary installation software. This will include the codec you need. Otherwise, check the support section of Kodak's website to download the file.

If this doesn't work for you, try the free VLC Media Player. This includes codecs that allow it to handle most video files without additional software.

If you insist on using Windows Media Player for playback or you want to edit your video clips, download the Combined Community Codec Pack. This bundles a selection of the most popular codecs in a single installation package – including several that you probably don't need, of course.

As with many things, the best solution is the most time-consuming. You could work out what codec you're missing, then download and install only that file. You can query what codecs are required to view any clip using the free MediaInfo utility.

Install and run the application, then drag-and-drop your video file on to the main window. It will reveal a huge amount of information about the file, including those all-important codecs. You can also configure MediaInfo to produce a summary of this information whenever you hover your cursor over a video file.

Once the encoding information is revealed, MediaInfo will usually supply a button you can click to jump directly to a web page containing the right codec for you to download and install.

With the correct codecs installed, your video file should play without difficulty.

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