Jim, just plugged a monitor into my HP win7 lappy, get desktop on the monitor & lappy same, 'just worked' - did think I would need to click an alert on lappy first , but no.
Have changed the screen on this lappy myself a few years ago, not too difficult, eBay, I think there is a little driver thingy for the screens that sometimes go's, mine was cracked so easy fault spotting
Hope this is helpful, regards Mick