1. Go to System Preferences and select «Expose & Spaces», enable spaces and create one row and four columns.
2. Go back to System Preferences, choose «Mouse» and disable «two fingers swipe to navigate».
3. Install MagicPrefs. Go to Swipes, set «two finger swipe left» to «Switch space right» and set «two finger swipe right» to «Switch space left» (natural -iPhone- scrolling :P).