Right-click on a blank spot on your Desktop and select "Personalize."
Click the link for "Screen saver" in the bottom right corner of the window
Use the drop-down list to change to another screen saver or (None) and then click OK.
If you want to actually remove the screen saver from your computer, first go to Control Panel > Programs and Features and see if it's listed there. If it is, select it and click "Uninstall."
If it isn't listed in Programs and Features, you'll have to delete the *.scr file. See the following for directions: https://www.screensaversplanet.com/help/guides/windows/how-to-remove-a-screensaver-on-windows-7-54