How to reverse your desktop wallpaper:
Mac OS X (10.4+)
1. Click the wallpaper counterpart.
2. Ctrl-click on the counterpart that opens in a renewed window and opt for Use Image as Desktop Picture.

Click the wallpaper counterpart and then fittingly click on the counterpart that opens in a renewed window.
Windows XP
1.
2.

Choose Save object as.
3. and keep the portfolio to your My Pictures folder.

Right click on your Windows desktop and opt for Properties.
4.
5. Select the Desktop label. Click Browse. and opt for the downloaded fancy portfolio.

Click Open, and opt for Stretch on the downright menu.
6.
7.

Click OK.