Upgrade your graphics card or play at lower resolution or setting nut looks of your system your using a mini ITX setup and wouldn't really use one for gaming as I find them more suited for home theatre systems
no error ever with Win8 Pro 64bit or Win8.1 Pro 64bit launcher runs as default admin modeSidenote: Recently, I have needed to run the game as an administrator because of some launcher error I have been receiving (running in admin mode is the only way I have managed to bypass the error) - not sure if this would effect the fps or not but thought i'd mention it just in case...
After seeing the link to your system you have been sold a mini ITX system.