Use paint! (All computers have paint) Paint works really good for sizing pictures. When your on paint and you have loaded your picture onto it go to the image tag on top then stretch and screw. Size your picture. If its a really big picture do 50/50 the larger the number the less it shrinks. Also most people do not know is the size your picture is in paint is the actual size of the picture! then I use photobucket.com to add pictures places. We use it on our forum to post pictures or the url to the picture. You can also make active banners using photobucket!
Anyway hope this helps! If I did not explain well let me know and I will do my best to help.
PS I only use paint to size pictures. It doesn’t work well for other photo editing!