you can use the onboard sound. It won't be as good as a sound card though.
And don't get a ide hdd when you've got 6 sata 3gb/s slots. Go for the WD 160gb 16mb sataII
...it has the same amount of space and will run alot faster then that ide drive...meaning your load times in games will decrease.
CPU: e6600 @ 3.2ghz
RAM: 2GB G.Skill HZ PC6400
Mobo: ASUS P5B Deluxe
GPU: Sapphire HD4870
Soundcard: Creative Labs X-Fi XtremeGamer Fatal1ty
HDDs: 250GB WD + 750GB WD + 2x1TB WD
Monitor: Samsung 226BW
PSU: OCZ GameXStream 600W
Case: Cooler Master Stacker
OS: XP Professional SP3
Mouse/keyboard: Logitech MX518/Saitek Eclipse II
Speakers: Logitech Z-2300