You need to resize the photos in a photo manipulation program first. Most people tend to run a screen resolution at LOWER then 1920X1280. If you take a typical 5 megapixedl photo. the resolution is a lot higher hence its massive on your screen as it cant be fitted on all at once.
Plenty of free programs out there that will do this for you if you google for it.
First you could use a program such as Irfanview to resize the images to make them a bit smaller.
Or, you could sign up for a free flickr account, and then just send people the link to your photos. They'll automatically be adjusted on the site and be put into slideshows etc.