I use IrfanView, too. I love it! It is free, easy to use, and it always works!
http://www.irfanview.com/
Directions--after you download it, click on "File" and then "Open". Choose your picture and click on "Image" and then "Risize/Resample" Choose "Set new size", mark your size and then make sure "Preserve aspect ratio" is checked. Then click on "File" one last time and then "Save as" to rename your picture.
HTH--not that you couldn't figure it out yourself, but someone did that for me when I downloaded it, and it totally erased the learning curve! I just wanted to return a good deed to the universe.
