Assuming you're using 32bit Windows XP click here do read the driver installation hints. The process should be much the same for sound cards.
BIOS updates need to be approached with caution, it's not that they're difficult, but they have the potential to kill the PC fairly comprehensively. BIOS stands for Basic Input Output System and if you get it wrong and corrupt it you lose all communication with the PC. The wisest approach with a BIOS update is "If it ain't busted don't fix it." If you have a specific requirement that needs the update go for it, check out your MOBO manufacturers websites for downloads and instructions.