THE XP AUDIO DRIVERS WORK FOR WINDOWS 7 TOO. Please follow ALL of my instructions and you'll have sound for your Optiplex Gx280 using Windows 7. Go to the official Dell site, then go to drivers download. Choose Optiplex Gx280 and audio as the driver type. Choose XP as the OPERATING SYSTEM and download the driver - it is titled R105155.exe (be sure you get the right one). Find the downloaded file and double-click to install. First the drivers will be copied on your computer under C :\Dell\ The system will attempt to install but it will Stop because you're not using Windows XP. - This DOESN'T MATTER. To install the drivers go to the computer icon on the desktop, right-click and choose Properties. Find on the opened window Device Manager and click it. Find and right-click on "Multimedia audio controller" and choose "Update Driver Software". Then click on "Browse my computer". Then use browse and click on "C:\" and afterwards choose "dell". Go to the bottom right corner, press "next" and your job is done!