my theory is that whenever u install software, the registry and DLLs are modified in such a way to optimize THAT application that u installed. if u install a dozen applications, then they are all trying to optimize those settings to their own benefit. and especially if u remove these softwares, then these settings will NOT reset to its original form (usually). therefore, your computer has layers upon layers of changes to the origianl OS settings, therefore these settings will not be efficient... and slowing your computer. my advice is to backup important objects and reinstall to your OEM settings, and install only the apps u need, and avoid "free" software or those that may not be written by professionals.