When you add and delete programs, download files, and save documents, changes are made to your registry. One of the main causes of a computer getting slower over time is corruption within that registry. Also, as you browse the Internet over the years there’s a likely chance that you’ll be infected with some sort of virus or Malware program that also causes the computer to run slower. Also just like you wish that guy who leaves the gym after busting a sweat would shower before sitting in the cubicle next to you, yourcomputer needs a good cleaning every now and then too because dirt and grime can cause your computer to work harder, run hotter, and thus operate slower. Last, it might not be your computer running slower at all as a bogged down Internet connection can make a computer run annoyingly slow.