Programs use DLL files that sometime do not unload from the memory when you shut them down. This can slow your computer down and kill the performance until you reboot your computer. To unload all of the unused DLL's from your memory without rebooting your computer, open the Registry and look for this string:
Right-click on the 'CurrentVersion' key in the left pane and select 'New->Key'. Name the key 'AlwaysUnloadDLL'. Right-click on the new key in the right pane and select 'Modify'. In the Value Data box type in '1'.