In Windows
- Press the "Print Screen" button.
- Open Microsoft Paint. To do this, click Start > All Programs > Accessories > Paint.
- Click inside the white part of the screen.
- Go to the Edit menu and select Paste.
- Click File > Save As.
- In the box that pops up, change the "Save As" type to JPG.
- After typing in a filename for your image, choose a location on your hard drive to save to, like the Desktop, and click "Save."
- Simultaneously hold down the ⌘-Shift-4 keys.
- Press the spacebar.
- Click the open window that you wish to take a screen shot of. The screen shot should appear as a file on the desktop labeled "Picture 1."
Please note that in Mac OS X 10.6, the file is "Screen shot [date] at [time]."