I've been using MS Photo Editor without a problem for this.
Just open the file, and click on Image|ReSize
You can adjust according to pixels, inches, or centimeters, in numbers or percentage.
What I usually do is open MS Explorer, so I can see the file's details, and MS Photo Editor. I open the file, reduce size and save under a different name, then put MS Explorer on screen, hit F5 and check the file size.
I save under a different name because once the file is reduced, it will become fuzzy if you enlarge it again.
Hope this helps