If you didn't install your audio driver after your Windows reinstallation, then does that mean you didn't install any drivers at all? To be sure, go into device manager (Right-click My Computer>Properties>Hardware>Device Manager) and look for anything with a yellow "?"
Windows will give you all sorts of crap if it doesn't like your drivers, or worse yet, if the drivers aren't there. Unless you've done so already, install your hardware drivers. Start with important ones like graphics and motherboard. Your PC might have also come with a support CD you can use.