1. Set external desktop speaker dial(s) pretty high - say, three-quarters of the way or more.
(Ditto with headphones, if externally adjustable volume unit on cord or headset - but watch yer ears!)
2. Adjust volume from slider on Media Player 9 or other, and/or perhaps inner audio properties card (Start menu > Control panel > Sounds applet.) Try some combination of these.
This is the basic advice one finds, when researching such things on the internet. It improved my sound alot to approach it this way.
That's all fer now, audio fans =)
Rock on ...;)