All builds of windows mobile 6.5.1 or newer (6.5.3) will not have the HTC Volume, because it's not compatible with the newer windows mobile. In other words if your start button is at the bottom of your screen you will not be able to get HTC Volume. If you want the HTC Volume you need to use a build of winmo6.5 or lower (winmo6.1).
An alternate solution is to use Setvolume (cab attached).
(I got it from xda:
http://forum.xda-developers.com/showthread.php?t=395695)