I posted this in another thread, but figured I'd stick it in here too so it doesn't get lost. It seems to be one of my most common PMs, so here is how to install a soundpack:
In the first pic, I have just downloaded a zipped soundpack to my Desktop:
I now unzip it, giving me the actual soundpack folder, called Sounds.
I now go into My Computer->C:->Program Files->HTC->Aces High II folder and see all the folders/files that go to the game. I locate my original Sounds folder and delete it. Then, I copy the new, unzipped Sounds folder that's sitting on my Desktop(the soundpack) and paste it into my AHII folder that I just deleted my old Sounds folder from.
If I installed my soundpack correctly, when I open my new Sounds folder up to look at it, I would see this. The original Sounds folder we already deleted is empty by default. If we were just adding a couple new sounds to the default ones, we would just drop them into our original Sounds folder, but since we are adding an entire soundpack, we are replacing the entire Sounds folder.