Pics for desktop background are too big. How do I change size to fit?

Hi demetman, 

Welcome to Microsoft Answers Community site.  

Follow the steps below to set your desktop background and choose the picture to fit the display screen 

1. Open Desktop Background by clicking the Start button , clicking Control Panel, clicking Appearance and Personalization, clicking Personalization, and then clicking Desktop Background.

2. Click the picture or color you want for your desktop background.

If the picture you want to use is not in the list of desktop background pictures, click the Picture location down arrow to view other categories, or click Browse to search for the picture on your computer. When you find the picture you want, double-click it. It will become your desktop background and appear in the list of desktop backgrounds.

3. Under How should the picture be positioned, choose to have the picture fit the screen, tile, or be centered on the screen, and then click OK, here you can choose fit the screen.

Reference Microsoft Article: http://windows.microsoft.com/en-us/windows-vista/Change-your-desktop-background-wallpaper

I would also suggest you to check for these Microsoft Windows Help & How - to Articles:
1: Change screen resolution
2: Getting the best display on your monitor
3: Change your desktop background (wallpaper)
4: Customizing the desktop: recommended links 

Let me know if that work. Good luck!

Hope this information is helpful. 

Thanks and Regards,
Vijay KKS