Microsoft has recently released official bing screensaver with Bing Screensaver which consist of some amazing pictures being used a bing search background pictures. We have just installed the same it has some really good nature, landscape images.
You can install this screensaver and use it on windows xp with sp2, vista and windows 7, with the following hardware requirement.
512 megabyte (MB) RAM or higher
500 megahertz (MHZ) processor or higher
50 megabyte (MB) of free hard drive space
After installing bing screensaver, you will find the bing screensaver listed in dropdown under screensaver settings.