One of the easiest fixes is going to be running a scan of it. It could be malware, or even a virus slowing it down. If nothing comes up, cleaning it out with a can of air is the next best solution. Dust is very bad for a computer and it can cause it to overheat and/or slow down. While you are cleaning it out, go ahead and make sure all the cords are plugged in. However, if your computer runs slowly, but it works, it probably isn't the cords. That's what I would do.
