Depends on your memory type. Given you only have 256, im assuming you have good ol' SDRAM, and a P2 or a P3, so you might need a whole new system.
Assuming you dont have a P2, or even a P3 which could be a bit slow, and you have an E-Machines that is just built with the minumum, you can easily upgrade it with new memory, which is cheep nowadays. I have 4 gigs in my PC, two 2-gig sticks, each costing $200 bucks, which isnt a lot for how much memory it is.
Its REALLY cheap if you have old SDRAM, and you could get it for probably $20 per 512 chip.
And if your that... uneducated, let your parents check everything before you blow their money on something, im sure they wouldnt be pleased about it.
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Crazy.
Toys in the attic, I am crazy.
Truly gone fishing.
They must have taken my marbles away.