|You're hurting your chances to get help by starting multiple threads.|
You need to learn how to research. The specs to ALL the systems you've been posting about are available at the manufacturer's websites - eMachines, HP, Compaq. The eMachines is the obviously the newest of the 3 & that is the one you should be concentrating on. The HP is outdated but not nearly as old as the Compaq. The Compaq is so old it should be in a museum somewhere.
eMachines are notorious for using weak Bestec power supplies, so it's very possible that's the problem. But you didn't state that you cleaned inside the case until now. Hopefully you didn't use a vacuum because if you did, all bets are off. Vacuums create static electricity which can easily fry electrical components. And if you took the heatsink off the CPU to clean it, it's very likely that you didn't replace it correctly. You need to explain what you did, in detail.