The Print Screen key, labeled Prnt Scrn on the Inspiron 1525 keyboard, is the universal key in Windows for taking screenshots. However, Mac OS X uses a much more arbitrary key-combination; the Keyboard shortcut is Command-Shift-3. Unbeknownst to many, OS X allows you to change many system shortcuts, including the shortcut for Screenshots.
To change the shortcut:
1) Launch System Preferences
2) Open the Keyboard Preference Pane
3) Click on the Keyboard Shortcuts tab
4) Click the Screen Shots option in the left pane.
5) Double click on the shortcut for “Save picture of screen as a file”
6) Tap the Prnt Scrn key to set it (F13) as the new Screen shot shortcut
Now when you hit Prnt Scrn a screenshot will be saved to your desktop. Enjoy!