I seem to have the same problem.
I just got my HP Probook 4440s NEW in March 2013 for online university.
Windows 7 Home Premium
SRS Premium Sound but no audio control panel.
I hear loud enough system sounds but all media audio is very low.
I understand this laptop isn't marketed for entertainment though i need it for listening to presentations and lectures along with tutorial videos.
The speaker in the taskbar is at 100% but it still sounds like it's at 15%!