Nice photo!
I'm somewhat surprised that the Canon software can't open the 550D's image files. Have you checked the canon website for the latest version?
Have a look
here. You can limit serches to specific OS's and languages.
Canon software can be a bit odd. They need the software that was supplied with your camera to be installed and present on your hard disc in order to install updates (all the installers are just updaters so you can't just download the latest version and do a clean install).