...but we need to know the model number of the machine, whether it is standard ATX, mini, or micro etc. Also Emachines uses marginal power supplies that are barely sufficient for what is installed, plan on getting a new one. Here's a cheap upgrade:
Don't count on it being 550 watt (in reality) or quiet, but it should be all you'll need for a while.
I have an older E Machine that has an AMD XP Athlon 2400 and the board is only good to upgrade the chip to an Athlon XP 2600. As that next to broke is my usual state, What would be a good upgrade for my board that will be able to use my curent XP 2400 but will be able to up grade to a better processor, say a 3200.