I opend up my computer, and put in another 512 of ram, and now my computer won't even start. I took it out, but it still didnt start, i checked all the wires, their all in the proper place. The only thing that i think i did wrong, was the button at the back,(red one by the power switch) that you can move up and down, that changes the voltage. That was moved and tryed to turnon the computer, and that didnt work, so that might have fried somthing.

Yeah you might have fried it.

Try replacing the fuses and then see if it works

If your line voltage is 230V and you switched it to 110V you may have blown the fuse in the PSU. This fuse is PC mounted and you will have to pull the board out of the case to access the solder joints. There are capacitors on this board that will hold a line voltage charge for a long time, and if you accidentally discharge this to your body it could be dangerous.

If you are not familiar with this type of repair I would suggest purchasing another PSU, to have a tech do this will cost as much as a new PSU.

yeah replace the fuse in the PLUG only (safe). Never open up a PSU. Get a new one, they arent that expensive.