It's taken a very long time, but you've finally found and downloaded that audio or video file you've been looking for. So it's particularly frustrating that it won't play. At all. But why?
You could try downloading the file again, just in case it was corrupted. Maybe using another media player would help. How about installing a new codec pack? Troubleshooting media problems is tricky, and you could spend hours trying to figure out the problem.
There is a quicker alternative, though. Just open your audio or video file in MediaInfo, and you'll see lots of technical information about it: video and audio stream type, codec, aspect ratio, frames per second, sample rate and more.
If the file is broken - a missing video stream, say - then you'll see that immediately, and won't have to waste time tweaking your own system. And if it's just using a codec that you don't have installed, then you can quickly grab the latest version, and hopefully fix your playback problems right away. (There's even a "go to the web site of this video codec" button, so it's only a single click away.)
As a bonus, MediaInfo also displays file tags: album and track name, performer, composer, publisher, whatever it might contain. And wide support for video and audio formats means it'll work with just about any file type - MKV, OGM, AVI, DivX, WMV, QuickTime, Real, MPEG-1, MPEG-2, MPEG-4, DVD (VOB), OGG, MP3, WAV, RA, AC3, DTS, AAC, M4A, AU, AIFF and more.