for start what graphics card have you got??
Also my guess in changing the rendering is probably changing the quality of like characters and environments/textures.
PSN: kurosagi01|steamid: phalanx-88| xfire: itachiasuka
Laptop: HP Compaq 6735s
AMD Turion X2 2.0GHZ|4GB DDR2 667|250GB HD|ATI Radeon HD3200|Windows 7 Ultimate 64-bit