Make sure your speakers are powered. Unpowered, walkman style, speakers won't amplify the sound as necessary.
Try double clicking the speaker icon on the bottom right of your screen (near the clock) and making sure that the volume is high there. also make sure that the volume is high for 'Wave' and 'CD/Video In'.
Check that your cable from your pc to your speakers is not damaged.
Check the volume levels on individual applications are set to high.
Hope this is helpful.
David, February 2007