Thanks. I was just curious if they are all pretty much a standard size and they generally all fit. NewEgg has this cheap one and it says “good for emachines” but it is too cheap.
For the most part, yes they are all a standard size, though there are certain considerations.
Some of the newer motherboards require a 24 pin plus, also called a 20 +4 pin, meaning that it fits the older 20 pin and also the newer 24 pin, then they also have a 4 pin CPU power plug.
My advice is to look at your current motherboard and see how many plugs go from the power supply into the motherboard and how many pins are on each, that will help you figure out what type you need.
If it has just one plus going into the motherboard than any ATX standard power supply should work.