I cannot change my screen

(assuming you have windows)
it sounds like you need to get a driver for your video card. right click on my computer and select manage. then go to device manager. the model number will either be under display adapters or under unknown devices. if you can't find it go and download siw. under that program go to devices and look for your video card info in the two aforementioned places.

the next step is to go and download drivers for your video card. go to the cards manufactures web site or just put the info into Google. they will be located under drivers or support. download. scan with an anti-virus and install.