here will do :)
if it's windows XP then right click anywhere on the desktop, select properties. then click on the screen saver tab and in the drop down box select "my picture sideshow"
if you then click on settings you can change a few options about thing like the duration the pics will be shown.
Also as default it will show all the pictures in your my pictures folder, if you only want a select few to show then you will need to copy them into a separate folder and tell the screensaver to look in that folder instead (also on the settings page)