I bought a PC with a DVI and VGA cable port. I hooked up 2 monitors, went into control panel and extended the displays the mouse only stays on the DVI monitor. Does DVI override the VGA signal? or what could the issue be?
To start with negatives, no, DVI does not override VGA, and what is more, the fact that your computer gave you the option to extend the desktop means that it detected both screens, so it's not a matter of a faulty graphics card...
So, what other possibilities are there? I suppose it could be a resolution/refresh rate problem. For troubleshooting purposes, set the resolution quite low (say, 800x600) and see if you get a picture on both screens, then work up from there.
Less likely, but still possible, is that your second monitor is set to accept the signal from the "wrong" input, which would result in a blank display.
it can be your monitor problem, try the setup on another monitor
if the monitoris detected then you can enable it, if not then check cables...
it can be also graphic card problem,you can use either the VGA or the DVI-VGA but not both because one set of hardware for converting the digital video signal to analogue VGA
Which version of Windows?
Download and install the free version of DisplayFusion from this link:
http://www.displayfusion.com/Compare/ and let us know if it cures the problem.