If you want to capture an image of what is on your computer screen, you can use the Windows operating system's Print Screen feature. Saving a screen shot as a JPEG file is a simple process that makes it much easier to send, transfer and edit images. JPEG is an almost universal image file type, and it can be opened in most photo editing programs.
Capture a screen shot by hitting "PrtScn" on your keyboard.
Open MS Paint. If you have a Mac, open MacPaint or Paintbrush. Go to the "Edit" drop-down menu and select "Paste."
Click to the "File" drop-down menu and select "Save." A box will appear asking you to name the file. After typing the name, open the "File Type" drop-down menu. Select "JPEG" from the list of file types.
Mac OS X does not come with MacPaint. You can download Paintbrush for free.