Hi (Dan here)
Hardware in computers age.. It may be a problem with heat from something, that causes the CPU to throttle, slowing things down. You can always download something like CPU-Z and Core Temp to see how the CPU is acting. Watch the temperatures carefully when running games and such. In some cases old computers thermal paste, the conductive material between the heat sink and CPU dries and crumbles, causing the CPU to overheat more easily. Replacing thermal paste on a laptop can be hard...
You might wanna also wanna try to reinstall windows fully.
And/or use this guide (It doesn't require a reinstall, but I'd advice it)
http://www.overclock.net/t/1156654/seans-windows-7-install-optimization-guide-for-ssds-hddsThe first time following that guide it might take you a couple hours.. But it's a very good tool, and make sure you read everything thoroughly.
(If the computer all in all runs pretty alright, and isn't too old, it can in some cases be a good investment to buy an SSD (Solid state drive) and replace the hard drive, since old hard drives can also slow down over time. SSD in some cases helps a lot, incase the other components are still in a pretty good condition)