First move special photos you have downloaded to your computer and wish to use as a screen saver into a new folder, one named, say, MY-ALBUM.
Now click on Start and open Control Panel. Choose the Appearance and Personalization option. Under Personalization, click on the line that reads "Change screen saver."
A dialogue box labeled Screen Saver Settings should appear. Below Screen Saver, click on the arrow to reveal a menu of options. Choose Photos. Click on Settings and then on the button labeled Browse. Arrow down until you locate the MY-ALBUM folder. Select that folder and click on OK.
You now have the option in the dialogue box "Photos Screen Saver Settings" to adjust the speed of transition from photo to photo on the screen saver: slow, medium, fast. You also can elect to shuffle (randomize) the photos. Make these selections, then click on Save.
Your selected photos now should become the active screen saver on your computer.