First off.. I get all the hate towards Windows 8. Really I even believe most of the people here understand it. But here is a guy asking for help and a possibly solution, so quit being a ******** and help the guy.
Second.. Currently running Windows 8 Pro, and SW:TOR is running perfect. Never had any issues with it, however I didn't install it. I simply made a complete backup of the installation and moved it over. So either it's an issue with the installation, bad drivers, or you missing a software component the game just forgot to tell you about (like the million versions of .NET stuff).