Sound card problem.

I recently formatted my PC with Windows XP SP2, but I've had a little problem on the sound card. I got all functioning (graphics, internet, ...) but the sound card doesn't seem to work properly. I went to HP's site (my model is a HP Compaq Dc5100) and downloaded all drivers, but when I installed Soundmax program (which previously did work on my computer) it said 'driver not found - reinstall and run program again' or something like that. So, I went to Device Manager and it had a yellow question mark on 'Multimedia Audio Controller'. I've tried various times installing the driver but the outcome is always the same. I was wondering if anyone here could give me any help...For further details of the PC:
http://i41.tinypic.com/2urtob6.jpg
http://i41.tinypic.com/2v1aurt.png
Note: As I am from Portugal, some words in Belarc Advisor MAY BE in Portuguese.
Thanks in advance.