My CPU is not supported as well: Intel Core Quad Q8300 - Microsoft Community
Which CPU upgrade? Intel Core 2 Quad Q8200, or the Q6700?
Intel's Core2Quad...Finally Obsolete? - YouTube
Restored Dell OptiPlex 780 Small Form Factor Desktop PC with Intel Core 2 Quad Q8200 Processor, 8GB Memory, 2TB Hard Drive and Windows 10 Pro (Monitor Not Included) (Refurbished) - Walmart.com