On to the CPU
4. Does your CPU work?

There is only one good, reliable way to test this: drop your CPU into a known good and working system. Use a friend's, a neighbor's, roommate's, hallmate's, coworker's, or whomever happens to have a system that will take your CPU.

If your CPU allows this known good system to power up, you know that it is good, and it is not the cause of your problems.

If not, you'll need a new one. As above, it's likely that this is your only problem, and once you get it replaced, you'll be good to go.

Note that I did not say to try another (known good and working) motherboard. The reason for this is that there are too many other variables at play: does the RAM work? does the video work? is the power supply work? These questions will be addressed later.
5. Does your memory work?

There are two (probably equally reliable) ways to test this, although one is riskier than the other.

The first is to take your memory and pop it into a working test system (perhaps the same one you used for the CPU) and, again, see if that system powers up.

If it does, we know the memory is good. For good measure, test all of your sticks in all possible combination, just to be sure that it's not a pair of sticks not playing nicely together.

If the good system fails to power up, you have bad memory and need to replace it.

The other (and riskier) way to test memory is to take known good and working memory and put it into your motherboard. This is riskier because the possibility exists that it is the motherboard that is bad. It is not unheard of for bad motherboards to kill good sticks of me