I do alot of photography work and edit many photos either through Lightroom or Photoshop and ive noticed that when I view my exported photos (JPG) with the native Windows (7) Photo Slideshow app everything becomes more saturated and sharper than when viewing in non-slideshow mode. Ive done alot of searching and I cannot find a reason why this is happening. In some cases I actually like the way the photos look in slideshow mode versus not and Id like to apply whatever Windows (assuming Windows is doing some kind of post-process effect on purpose) is doing to the actual photo edit in Lightroom.
Preferably like to see no change when I enter slideshow mode but that might be a limitation with Windows 7, im not sure. I would like to know whats happening though.
I currently have a Dell U2410 Ultrasharp monitor with an Nvidia 670 graphics card.
That is because the slideshow app in windows 7 is not color managed and this monitor is a wide gamut monitor. Your probably sRGB images will appear oversaturated in non-color managed apps on that monitor. Only solution is to not use non-color managed applications.