AC3 ACM Decompressor for VirtualDub. The core is based on liba52, and it works with most any ACM client (VirtualDub, TMPGEnc, Avisynth, CoolEdit, etc). The only downside I´m aware of is that it tends to override DirectShow AC-3 filters, like Valex´s

If you´ve never installed the decompressor before, simply right-click on the "AC3ACM.inf" file, and choose "Install" from the popup menu. I don´t think it´s necessary to reboot, but it can´t hurt. If you get a scary warning that the program has not passed "Windows Logo testing" (which is quite true BTW), choose to "Continue Anyway."

To uninstall the decompressor, start Control Panel´s "Add/Remove Programs" dialog, select "AC-3 ACM Decompressor", and press the "Add/Remove" button.

If you have installed a previous version of the decompressor, I recommend you uninstall the old version as described above, and reboot Windows before installing this version. (It´s probably not necessary to do all that, but again, it can´t hurt.)