FPS problem on good pc

Hello,most of the time in game Im getting about 17-25 fps no idea why since my specs are:
Radeon hd 69xx series 2gb
Amd Phenom II x6 3.30ghz
8gb ram
Windows 7 x64 (was running before on windows 8.1 x64 and had the same problems)
Risen 3 runs smoothly but 2 dont D:,pls help.I tried reinstaling game and nvidia psyhx no results :(