In your display properties/settings/advanced there should be a thing called nView. If there isn't reinstall your drivers. nView can do a fair few things, mainly, it can clone your main monitor screen so that you see the exact same thing on your second monitor.
If you want to extend your desktop go to display props/settings and you should see 2 monitors, one being greyed out labled 2. Click on then, then tab "extend my windows desktop onto this monitor" then press ok. I'll then activate your second monitor.