Bad fps on Elder Scrolls Oblivion on new pc

My specs are as followed;
-Athlon II x4 750k Black Edition 3.40GHz
-Sapphire R9 270 2gb
-Corsair Vengeance DDR3 1600Mhz 2x4GB Dual Channel 8GB kit
-500w Corsair Bronze
-1TB WCD Hard drive
-Gigabyte GA-F2A88XM-D3H Motherboard
-Windows 7 Ultimate
-BitFenix Comrade Case Midi-Tower

Hello

Basically i pull my old copy of Oblivion off the shelf to have a go at again but i'm getting a 30-45fps on high and even on low. My old pc that played it was crap compared to my new one, so why the bad fps.

Any ideas people?

Thanks