According to webopedia.com troubleshoot is to isolate the source of a problem and fix it, typically through a process of elimination whereby possible sources of the problem are inverstigated and eliminated beginning with the most obvious or easiest problem to fix.
In my experiences, computer problems are the worst possible kind of problem for one to deal with. Anytime that I've ever experienced any computer problem I've always turned to searching for the solution online. I found a website that has common computer problems and solutions, check it out: everythingcomputers.com/troubleg.htm
As I was researching about this topic I didn't come across to the specific reason why computers troubleshoot. My assumption is either because of virus, software issues, or hardware issues. Whatever the case may be one can always obtain help online or through a technician in a store like Best Buy or Staples.