Windows 7 Black screen

Hello, my name is Vytas and I need help with installing windows 7, I got Dell Precision™ T5500 it had windows xp before and i tried several times installing win7 true usb boot, the progress works fine everything is ok, but after finalyzing and waiting to load the main screen its just stays black, machines is still on, but the screen goes black. Have no idea whats wrong or what to do.