For years, I’ve had OSX running on my old Dell Optiplex GX520. First I started with Tiger, then I eventually was able to get Leopard running up to version 10.5.8. however, that was as far as I could get it working. Most troubles upgrading kept coming from the GMA950 Video. Thankfully, someone at InsanelyMAC, posted a guide recently on how to get this machine all the way up to 10.6.6 Snow Leopard. So, make sure you have a valid license, then hit up the link to get your Mac on.