Just wanted to mention that if your CPU runs too hot, there would be a performance loss through Thermal Throttling. If your system starts off fast and then starts to get slower then I would look into what the CPU temp is measuring to rule out a thermal problem. This problem is more common with older processors, however its possible if the CPU heatsink is clogged with lint/dust bunnies or a heat pipe fails on a better than cast aluminum heatsink. A CPU that runs too hot will underclock itself to run cooler and this causes the system to lag and become noticeably slower. Some systems even shutdown if they reach a specific temperature as a means to protect from CPU or APU meltdown, however the thermal throttling usually keeps a system away from the shutdown temperature. A tool like speedfan can be used to look at system temperatures.
