Why not download the FREE programme from FastStone which will not only open them but also has the ability to edit them (with a little help from you).
Lots of other features available in the programme too.
Just a bit of information from their web site:
FastStone Image Viewer is a fast, stable, user-friendly image browser, converter and editor.
It has a nice array of features that include image viewing, management, comparison, red-eye removal, emailing, resizing,
cropping and color adjustments.
Its innovative but intuitive full-screen mode provides quick access to EXIF information, thumbnail browser and major functionalities via hidden toolbars that pop up when your mouse touches the four edges of the screen.
Other features include a high quality magnifier and a musical slideshow with 150+ transitional effects, as well as lossless JPEG transitions, drop shadow effects,
image annotation, scanner support, histogram and much more. It supports all major graphic formats (BMP, JPEG, JPEG 2000, animated GIF, PNG, PCX, TIFF, WMF, ICO and TGA) and popular digital camera RAW formats (CRW, CR2, NEF, PEF, RAF, MRW, ORF, SRF and DNG).
Direct download link is here