Onboard sound, and Sound card

Hello,
I recently got a new computer that I built myself, and I can't figure out this problem and it is likely to slay me if I don't fix it. My specs of this computer are: 4 gigs of ram, 2.5 ghz dual core processor AMD, 250 gig hard drive, nothing on it so like 225 gigs still; and I didn't have the money yet for a video card, but I don't know if this could be the problem, but an Nvidia GeForce 4000 MX. xD...
But yeah, when I play music and I browse sites and stuff like that, the sound will be static-y and sound bad if I start moving stuff around or things load. So then I went to youtube, and the videos are really really choppy, and the static is consistent, and it just sounds bad. I'm wondering if anyone knows my problem, and can help fix it. Thanks. ^^
Oh and I'm using a Sound Blaster sound card, that I bought seperate, because I couldn't get the sound device that came with the mother board to work.. Which is a K9A Platinum MSI Crossfire.
For the onboard sound, I installed the driver from the CD, but it didn't help. It still said that there were no drivers.. And re-installing didn't fix the problem.. Can anyone help? Thanks