Two routes to go here.
Blow it out good with canned air. Slide a tooth pick down in the fan blades so it doesn't spin while getting blown out. Reason being Intel CPU chips have a self defense mechanism that will throttle back the chip when it's getting too hot. Blocked air flow can cause over heating.
The other is to clean out all those junk files your computer collects that can slow things down. Check this list of software I use to keep my babies all happy.
PC Cleanup Toolbox
Stay out of black viper. It's for advanced users. Edit the wrong service and you can find yourself locked out of your system. Also you may want to look for find junk files at another web site. Some have been complaining that cnet has gone to the dogs. I don't have any problems with them but better to be safe than sorry.
When you install any software make sure you use the custom install selection. That way you can disable any junk that they want to install that is crapware.