The way I see it you have a few options to try out first before you're installing Oblivion again.
1 - Update Windows7 (install any Service Pack there is available)
2 - Check out the vendor of your computer/motherboard for any updated software you can find
3 - Also update the software of your sound card (sound card is often integrated on the motherboard these days)
4 - Don't forget to visit http://www.nvidia.co.uk/page/home.html or http://www.amd.com/se/Pages/AMDHomePage.aspx (AMD homepage) of the latest drivers for your video card
If that's not working for you please post your results here so that anyone else can assist you. :user: