Also, some registry information may be shared and uninstalling or deleting it could make other software not work, though this is not usually how things are done these days - I only mention it for reference. You can use registry crawlers to find Mixcraft, Acoustica or other related entries and remove all you have found but I'll wager your registration information won't be among those entries.
It could be literally anywhere and in any form in the registry. Many (if not most) software developers use purposely hidden or obfuscated registry information to hold registration keys, serials and similar information. The reason is software piracy and skirting registration. You are opening a can of worms here and it may be that Acoustica won't share that information in an open forum.
