You don't get to be the longest-running science fiction television series in history without a few casting changes. Time-traveling show Doctor Who debuted on the BBC in 1963, and since then eleven different actors have played different incarnations of the Doctor. This Windows 7 theme starts with the very first Doctor and displays images of all the Doctors to the present...with glimpses of his time machine, the TARDIS (inside and out) over the years.

The Doctor himself is the only constant in Doctor Who's ever-shifting temporal and physical settings, so this theme concentrates on the titular Time Lord. It's a walk through TV history, starting with the First Doctor (William Hartnell) in dignified, grainy black-and-white, and showing a couple images of each Doctor in order, ending with the dramatic lighting and special effects around the Doctors of the twenty-first century. The sharpening details and increasingly vivid color reflect advances in photography and video technology.

This theme includes both the favorite Doctors and the largely forgotten. The ever-popular Fourth Doctor (Tom Baker) exudes as much intelligence and quirky charisma as ever. Images of the moody Ninth Doctor (Christopher Eccleston) herald the uptick in special effects that came with the series relaunch. The images of the mercurial Tenth (David Tennant) and pleasantly batty Eleventh (Matt Smith) Doctors are among the most striking. But these are just highlights...if you were a big fan of, say, the young and blond Fifth Doctor (Peter Davidson), or if you always thought the Eighth Doctor (Paul McGann) of the ill-received 1996 TV special deserved another chance, you'll find your Doctor here.

Fans will recognize many of the sounds in the Doctor Who Windows 7 theme. For instance, your PC will shut down to the sound of the TARDIS moving. We'll let you discover the others on your own--after all, the spirit of adventure is one of the things viewers love about Doctor Who. One warning: Don't be alarmed when a certain villainous catchphrase blares out as you empty the Recycle Bin.

Note: To install this Windows 7 theme, unzip the downloaded archive and double-click the themepack file within. Windows does the rest.

--Laura Blackwell