Poor sound quality after recovery

I recently had to run a recovery on my hard drive after contracting numerous
viruses. After doing so, I have noticed that the sound quality on my PC has
diminished considerably. Prior to the recovery, the quality was fantastic,
but now I am experiencing seriously distorted feedback (very tinny and
echoey, and a poor sound balance).

This happens when playing music on Media Player 10, when given the sign in
greeting for AOL, and when I play a computer game... pretty much any sound
the comes from my speakers, basically

Even when I bought the computer brand new, I never experienced this problem,
and I'm stumped what could be causing it. I have gone into control panel and
set the speaker setting to those relevant to my PC, and checked to make sure
all the relevant volume controls are in relevant balance, but to no avail
whatsoever.

This is driving me insane, can anyone offer any suggestions (not too much
jargon please, I'm not too clued up on computer lingo)?

I have a Medion laptop, model MD2592.