There is software , some built in the OS and many after market that can do in system "house cleaning " and testing. One example is PC Alert. It shows up as a small open eye in task bar and when We move mouse over it, it reads out my CPU temp. If I right click it and go to the main page, I can test the inter system of every function of my computer as well as all the external systems as well. An inter system test, for example, could be a memory map, showing what is in memory at that moment. Another is a test of my fans, speed, efficiency etc. It basically is the way you find out if the inter system is working with out any problem and is a big help when you do have a problem in finding a fix for it.