Slow problem is a common event for Windows user. It's not all related with hardware, registry, viruses or spyware!
"No matter how fast or shiny computers might be when they're new, they all seem to get slower over time." Microsoft claimed that on their technical forum(Windows 7 forum).
In fact, Windows built-in a lot of services and startup item start with system. So if you want a faster computer, you need to disable some of them first.
I saw an article before. It descripe how to make your windows faster.
-------> How to Speed Up Computer
If you still don't know how to disable services safety, Click here to fix Windows SLow
by professional tools.
Any problems? Welcome to discuss with me! Enjoy it !