This application is a AC3 ACM Decompressor for VirtualDub.The core is based on liba52, and it works with most any ACM client (VirtualDub, TMPGEnc, Avisynth, CoolEdit, etc).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, it is recommended that 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.)