I uninstalled Microsoft SQL by mistake and I don't know how to get it back!!!?

Okay, I installed Pinnacle Studio 10.5 and had a problem with some SQL thingy - it said "uninstall and reinstall" so I opened up the control p and uninstalled the only thing that I could find that said SQL!!! Too bad that I am usually really good with computers, but this has me stumped b/c I have no idea what SQL is, and why I need it, and why it is screwing up my computer and Pinnacle. Now I get an error that says "Your sql server installation is either corrupt or has been tampered with..." Please HELP!!! I don't even know what I did, so I certainly can't fix it. BTW, I am running windows XP.