You may have pressed the key combinations on the keyboard to flip the computer screen and may have made some changes in your computer settings without realizing it. But it is never an issue, you can flip your computer screen back to normal in three different ways.
1. Flip the computer screen using keyboard combinations.
2. Flip the computer screen using Display Settings
3. Flip the computer screen using the Graphics Option.
Method 1: Flip the computer screen using keyboard combinations.
On the main windows screen, Press and hold the key combinations CTRL and ALT key while you press the UP arrow key or the DOWN arrow key on your keyboard to flip the computer screen to normal. (you can also use the LEFT and RIGHT arrow key to flip your computer screen)
Method 2: Flip the computer screen using Display Settings
Right click anywhere on your main desktop home screen. Select the option Screen Resolution for Windows 7 and Windows 8.1 and for Windows 10 users, select on the option Display Settings. The Screen Resolution windows pops up and under the Orientation drop down list, select on Landscape.
Method 3: Flip the computer screen using the Graphics Option
This method is quite similar to the previous one, right click anywhere on your desktop main home screen and from the Graphics Options side menu, select in the Rotation option and from the side menu, choose Rotate to Normal.