Replaced memory no monitor

[rockyRad]

I removed the 128 mb and added 512 mb memory to the same slot in a Dimension 4400. After plugged everything back in pushed the on button which is very hard to tell if on or off. It is green and all lights in back are on. The monitor will not comeback. The DvD and CD Rom both work.

I cant tell if the the 4400 has come back on or the monitor just isn't working. I removed the flat screen and hooked up an old Dell monitor. The Dell monitor light goes green then yellow.

Help!

rockyRad

 

[Tmagic650]

This Dell memory may be proprietary. If the computer has only one memory slot and it came with 128 installed, it must be pretty old... You may be limited to just 256MB. Is the 512MB stick the same type and speed as the 128MB stick?