Gateway monitor problem

[dmh07]

I have an old Gateway desktop computer with a Gateway flat screen monitor. The display on the monitor started "shaking or quivering". I thought that the monior was bad so I bought a new LED monitor and connected it using the new cable that came with it. The display is the same. What can I do to fix this? I am not very tech oriented so please make the suggestion very simple to understand.

 

[scout_03]

it could be the graphic part on the old gateway system need name and model

 

[dmh07]

It is a Gatway 300 X.

 

[scout_03]

this is the only thing i found on this system made 10 years ago it got internal graphic see if you had a pci-e card that could resolve video issue that the link for the user manual http://www.retrevo.com/d/ds/progress?doc=f96dac810d0c0608b900ae50b495891d&rk=0.7854838885369583