OK. I have tried EVERYTHING I can think of. I have had my Gateway desktop for 5 years. I have never had any issues until I had to replace my graphics card. Now it won't power up. The fans run, there is a little orange light, and the disk driver light blinks. BUT it won't come on. I am at my wits end. Info I know (it was a gift and I am far from computer literate)

Gateway model GT4022
Windows XP operating system
3gb Ram
Nvidia Graphics card
It doesn't have a lot of stuff on it so I don't understand it. Please any help is greatly appreciated.

It doesn't have a lot of stuff on it so I don't understand it. .

first i don't see what that has to do with a computer not booting ,what is stuff
are you sure the replacement video adapter is compatible with your mother board,is it a agp card ,what model # on card ,what happened to the original card ,are you sure it was the card that went .
your mother board has on board graphic adapter also i think ,if so hook monitor to it