Celestia Portable provides a virtual planetarium for free. You can save it at any USB or extractable portable drive.
Celestia has a large database of planets, stars, and other cosmic bodies that you can visit by space and zooming.
With Celestia, you can see the place from Earth, and use it to see the heavenly bodies from different external perspectives.
Another great feature is the ability to increase the number of visible add-ons created by other program users.