I tried that first, but couldn't find a slider. Then I read your post and looked again but I couldn't find one. But this I time I opened the program from the start menu (rather than the icon), and noticed the PDF documentation file was in there. I read the thing and it said to adjust the volume with the slider (left or right). Hmm. Opened AVC again and there it was. DOH! Stop laughing, this senility thing isn't funny!
(if it had 'a been a snake, it woulda bit me!).