Well, try this:
You'll need to register, but its free, and should be quick.
Then just, while on Add Hardware, find that file once it asks for it.
If that doesn't work, defineitly go for the new Sound Card approach.
I'll do a search while you are downloading and trying.
This seems like your best bet:
Creative is always the best soloution for sound nowadays, and plus its Audigy, so is reletively new for the games stand point.
Plus, not a bad price. I'm sure you will agree. Just make sure you keep the driver CD kept in a safe place this time
Trying to hit two birds with one stone, your motherboard supports this type of RAM:
3 x 184-pin DDR DIMM Sockets.
Support max 3GB PC2700/PC2100/PC1600 non-ECC DDR SDRAM memory
So, I'd go for PC2700 speed which is the fastest it supports, and should be very cheap nowadays.
How much RAM have you got at the moment?