`across`: Up/down or left/right?
Which monitor/TV are you using?
Did you build from scratch or reuse come components, if so which ones?
In the meantime:
Check you are using the latest drivers and you have installed all the motherboard chipset drivers.
Check you have the monitor connected correctly.
Check the display settings in Windows and make sure you have the right resoloution and, particularly, refresh rate for your monitor.