If you are stuck with a "slow running computer", unfortunately there is not one single "remedy" that's guaranteed to work. The solution is to just try a combination of different things.
But having said that, there are some problems that are far more common than others. Here are 3 problems and their corresponding solutions for the most of-seen computer problems.
PROBLEM # 1) Registry
One of the most common is the registry. This is actually to blame for up to 90% of all Windows computer performance issues. The registry is the "central command" system for your system. Every time you add or delete a file, it gets added to the registry.
Remember – your Registry has to sort through all the old records of every file you've downloaded in the past to get the new files you are currently using. Obviously if it takes a long time to find it, this will cause delays.
Also, sometimes size is not the issue – it's simply that things are saved the wrong way, either by you or the Registry. Either way, the only solution is a "registry cleaner". I would recommend doing a "free registry scan" before paying just to make sure this is a potential issue. If your computer is older, more likely than not it's a faulty Registry that is causing slow-downs.
PROBLEM # 2) Error messages
Believe it or not, if your PC sends you error messages, simply typing them into a Search Engine in quotes should pull up the solution you need. It's almost guaranteed somebody else has had that exact problem … and you can just see what others have done to fix it.
REMEDY # 3) Get rid of programs
The reason for this is obvious-it makes more room. But do not forget to after go to the "Recycle Bin" and delete it there as well.