Have you been dusting the keyboard when all of a sudden things went pear shaped? Thankfully there is a way to
remedy this in Windows. This will work for Windows 7, 8, and 10.
Rotate Display with Keyboard Shortcuts
Hit CTRL + ALT + Up Arrow and your Windows desktop should return to landscape mode. You can rotate the screen to portrait or upside-down landscape, by hitting CTRL + ALT + Left Arrow, Right Arrow or Down arrow.