Optiplex 780 with add on graphics card

Hi Dell,

I have an Optiplex 780 which works fine except that any add-on graphics card I add doesn't work.

I've played with the BIOS settings, tried different older cards from Optiplex 760s and 745s (Geforce 210's, Geforce 9300, etc) but I cannot get any add-on graphics cards to work.  According to the original configuration it came with a graphics card installed when we got it but I cannot find that original one.

The built in DVI and VGA do work but they don't support high enough resolutions for the applications I'm trying to run and that's why I want to use an add-on graphics card (an old Geforce 210 would work fine.)

I have read online that some people say you need a more powerful power supply than 235 watts to run any sort of add on video card but that doesn't make sense since it came with a video card originally.  I'm not trying to do extreme gaming and using something like an old graphics card would be perfectly fine.

I'm an IT person who's built computers and supported them for 20+ years so I hope to get an honest answer.

1.  So how do I get an add-on graphics card to work with this computer?

2.  Do I need a more powerful power supply than 235 watts to run a add on video card?

3.  Are there any known resolutions with the Optiplex 780 to this problem?

4.  What knowledge do you have about this problem and its cause?

Thanks in advance.