In order to troubleshoot a computer that has so many interconnected parts the best approch would be to "divide and conquer" which means you will divide one complex problem into a number of smaller problems until it's small enough to solve.

• Make a list of all the peripheral devices that are connected to your computer
• Note where each one is connected and how it's connected
• Leave the bare minimum such as the Tower + Screen + Keyboard + Mouse.
• At this point you can narrow down the problem to either some of the previously plugged in devices or a more serious problem with the essential components.
• Let's say computer begins to power-up and then shuts down or you can hear the fan but nothing else happens. You can take a guess that it's a power supply issue.
• Let's say your computer is powering up but then you see some text and all of a sudden it freezes with partial text, in that case it could be a CPU overheating or some kind of problem with RAM.
• Let's say you can boot as far as initial operating system boot sequence but all of a sudden computer freezes or you get a black or blue screen with some text, in that case it could be something corrupted with operating system such as windows or max os and the messeges / numbers on a screen could give you a clue on what kind of error it is.