I hope I can answer your question are you referring to capsaters as capacitor if you are you can see the the blown capacitor at the top or on the side look for smoke damage..
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Second check the back of the power supply there is a red slider slider switch check to see if its on 120 volts not 220 volts
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How many POST Code Beeps are you getting? if its not booting up you should be getting POST Code beeps if your computer come with a mother board POST Code speaker, 1 beep = all clear, continually beeping = multiple of things bad memory or mother board or
video.is bad.
First off check which slot you put the memory in DDR 3 will fit in DDR2 but won't work. If your running DDR2 Single Channel memory in a DDR 2 dual channel slots make sure you put the single channel in the slot closes to the cpu the left slot .if you have 2 slots or if there is 4 slot the 2 closet to cpu insert the one DDR 2 in left slot leave the other one out then see if the computer boots up, if it does then shut down and insert the other one.
If none of this doesn't work part out the computer you may have a bad mother board. Dave