I haven't used any photo editing software lately other than Corel PhotoPaint and IrfanView. PhotoPaint is for creating images as well as editing them, so that might be a bit over the top for what you want. IrfanView is very good though. The latest version can display just about any kind of image and run many sorts of media files (you need to install the files called 'plugins' as well as the IrfanView program).
For Photos it can:
Resize - sharpen - add various effects - crop - rotate - enhance - reduce redeye - convert file formats - acquire images from a scanner - copy scanned in documents - batch convert (take a bunch of photos and resize them all in one go for instance) - create a slideshow - provide an e-mail photo option - give a good quality thumbnail display of all images within a folder.
So this would be my recommendation. Mr IrfanVeiw does include the option to install a Yahoo toolbar. You'll need to read the options carefully as they come up during installation if you don't want that. I don't suppose you can blame the man for trying to make a bit of money for such a good program. He's kept it free so far. A donation is optional.
Link to IrfanView:
http://www.irfanview.com/Other good photo editors are also free. They no doubt work very well. Some are given free in order to entice you into buying the latest versions. That's not to say they are limiting in any way however. They used to sell these, now free, versions a while ago.
Here's a link to some:
http://tinyurl.com/32lpv