Can audio (AC3) decoding be turned off?

Hello, I have a slow computer and most movies with AC3 sound are pretty much unplayble. So I was wondering is there any way to turn off audio decoding so that it's doesn't take CPU time? Muting or Lowering the sound volume to 0 doesn't help as the audio filter is still working in the background. Any ideas? Thanks in advance.

[adicoto]

Try to uninstall AC3Filter and use only the iviaudio.ax decoder. If you need more help, send me an e-mail.

[bspfan]

How can I install iviaudio.ax without installing Codec Packs or Intervideo products? Also as far as I know AC3Filter (ver.1.01rc5) is the fastest AC3 decoder and it's still taking about 40-50 CPU load so I don't see how Intervideo audio decoder will help but I'll try it anyway.