Viewing images using Windows Photo Gallery

I've noticed that some of my images when using Windows Photo Gallery don't seem that sharp but when I use another application such as Nero Photosnap Viewer the images are pin sharp and very clear. Is this something to do with the resolution that Photo Gallery uses? If so how can I change it?

I forgot to add that when using Nero it is shown as full screen but windows it is shown slightly smaller - perhaps that is the reason?

Thanks

Rob

I hope he does not mind but I used beginner's image "Test Shot" because of it's fantastic feather detail. Side by side on my monitor, both at 100% zoom, I can see no difference in the sharpness. My only comment is that the colour might be a shade darker in Photo Gallery than Photsnap.
I think because PhotoSnap opens as full screen, a zoom of 154%, you are not comparing like for like.

To be able to compare different viewers, you must make sure that the zoom factor is the same. Pictures are most truly represented when viewed at 100% zoom. This means that a pixel in the photo is also a pixel on the screen.

I don't think Windows Photo viewer is the best application for this purpose. I'm using the Organizer part of Photoshop Elements 6, which is a very good program, and also lets you tag and sort your pictures.