That's not enough information. Do you mean that you have win7 with one monitor, attached another, and the new one didn't show anything? That's easy to fix with Display Properties. Right-click on your desktop, select Properties, go to the Settings tab, click on the picture of monitor 2, and check the box "Extend my Windows desktop onto this monitor."
If you mean something else, please give more detail. I'm not sure how "win7 upgraded to win7" is relevant to adding a monitor.