Only booting when no RAM installed at all

Hello there!

I have an Asus Essentio and it began not booting all the way up - fan going on and off and power light blinking.
We tried a new power supply to no avail.
We discovered that it would stay on if we took out the memory cards (3x2GB ddr2) so we thought faulty memory cards and got new ones. Still wouldn't boot up.
I tried only one card and tried it in each slot but nope.
I also tried leaving cards in but unplugging power to CD/DVD (even though the new powers supply hadn't helped) but no again.

I have no idea what to try next!

Thanks in advance,
Melanie

 

Which model (from the white sticker on the back) Essentio do you have?
Does it beep with no memory modules?

 

Very possible that you got the wrong type of RAM modules.