I am rebuilding my computer (XPS 400) after a hard drive failure, installed OS, (Windows 7), and other programs without issue. I have a relatively new U2312HM monitor, (about a year old), Installed drivers and Power Nap software from disk, now the monitor randomly disconnects and connects again while working on the computer. This is not a screen saver issue, it happens when I am active on the computer. Then it would go blank and not come back on no matter what I did with the mouse or keyboard. I have had to do a hard shut down. Computer boots up and all is fine, then it starts over again. Monitor is functioning okay, press menu buttons, get message not getting input from computer. I have a NVIDIA G-Force 6800 video card (original to computer)

Of note, I uninstalled power nap without any difference, also I am not running any graphics demanding programs. I suspect my graphics card is going....anyone have any thoughts?

Computer specs XPS 400, CPU speed 3.0 Ghz, 4.0 GB RAM

According my computer specs, what card would be appropriate should I need to replace it?