The core is based on liba52 and the open source FFmpeg ac3enc code by Fabrice Bellard, and it works with most any ACM client (VirtualDub, TMPGEnc, Avisynth, CoolEdit, etc). The only downside IÂ´m aware of is that it tends to override DirectShow AC-3 filters, like ValexÂ´s.
If youÂ´ve never installed the decompressor before, simply right-click on the 'AC3ACM.inf' file, and choose 'Install' from the popup menu. I donÂ´t think itÂ´s necessary to reboot, but it canÂ´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 PanelÂ´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. (ItÂ´s probably not necessary to do all that, but again, it canÂ´t hurt.)