C&C Generals + Zero Hour DirectX 8.1 problem

This is sudden and shocking. I've 91 hours between these two games and recently reinstalled them on a computer I've played them on before. My little brother was playing it, then suddenly it shut the game off and popped up an error that read: "Please make sure you have DirectX 8.1 or higher installed. Also verify that your video card meets minimum requirements."

Having bought this thing after the year 2000, I'm sure the video card is good, plus I can play Sim City with the graphics on max and have no lag or loss. I've tried DirectX patches, uninstall/reinstalll, compatibility mode. Any ideas?