Query: Did your computer beep when it came on before the RAM upgrade? (most do)
Does your computer beep with the new RAM installed?
If not there may be an incompatibility with the RAM. If it does beep, there is either a power problem with the Power Supply or the Motherboard itself.
I have also seen IDE cables cause the computer to not turn on properly. Unplug everything and see if you can get it to POST at all. If it does POST then replace the bad cable.
You could just need to replace the Motherboard in the end, but be warned if you replace that and want to keep your HDD and current OS you will have to do a trick to get it to boot. I have done this many times as I work in IT for small businesses.










