DirectShow decoder needed, already tried AC3 filter

I have an issue with getting my audio to work on DivX or Windows Media Player. I downloaded the AC3 filter once and it worked after that, but once I turned my computer off and back on again later-the same message appeared. I have now downloaded every type of filter recommended on these forums. I have even downloaded gspot which gave me these results:

File Type: Matroska media file(.MKV)
Mime Type: video/x-matroska

Partial Render Failure: Following is the error reported by DirectShow
0x00040242: (unknown)
(Src) — >>(A) — >[DivX Decoder Filter]> — ( — >[Video Renderer]

If you know anything I can try please help. I would highly appreciate any knowledge you can offer me