Again, always overlooked or forgotten, Make sure you install the most up to date drivers and not to forget to install any drivers. Or, install the drivers that work best for your hardware, which is very common.

1. Updated drivers include fixes,forgotten files, performance enhancements that may not seem obvious to most people but they truly are there and have been proven to exist. Sometimes updates include fixes for hardware conflicts and firmware upgrades that can effect input consistencies.

2. Forgetting to install drivers is easy because windows does so many things automatically. Even make sure you dont forget to install .Net Framework and the one I always forget... DirectX which effects performance and no, not the version that comes included with games.

ATi Drivers

nVidia Drivers

Xbox 360 Controller PC Drivers

PS3 Controller PC Drivers