To slow in my Pc

well, suming up, it´s to slow in my pc, i´ve just bougth it and i´m very very very disapointed with the frame drop that it has in my, the configuration is not that good it´s a intel pentium e5400 4gb of ram, intel familychipset g31/g33, but i´m sure it´s enought to play without lag. please i bag you some how make it work without frame drop, i´d love play it in 30fps at least.