Hmm right. Try this:
Open up Control Panel from Settings, and go to Sounds and Audio devices.
Under the Volume tab, where it says Speaker Settings, select Speaker Volume.
Here, check if all the sliders are equal to each other and one isn't louder than the other, as it could be a balance issue.
SECOND STEP TO MAKE SURE:
Then go to Volume Control in the task bar, and Open it up so you get the mixer. Make sure the play control is Balanced, and all the rest are balanced.
Go to File, Properties also, and select all of them that aren't there that could be related to the sound coming out of your speakers. For instance Wave/MP3, and make sure these are also balanced at the top.
If all this does the job, then thats great
If it doesn't then its more likely to be your sound card with a damaged connection or something
You can pick up a Creative Sound Blaster Live for cheap if your not interested in more than 4 speakers at a time, which simply plugs into a free PCI slot.
I hope this helps.