Chahil, the chief marketing officer of the Personal Systems Group, leaves HP (HPQ) at the top of its game. Since he joined the company four years ago, the company has taken share from rivals such as Dell (DELL) through a combination of operational efficiency and savvy messaging. For example, under Chahil’s watch HP launched an ad campaign called “The Computer Is Personal Again” featuring celebrities such as Serena Williams, Jerry Seinfeld, Vera Wang and Jay-Z.

In an industry where executives have traditionally focused on component costs rather than design and presentation, Chahil, 59, has always been something of a rebel. After stints at IBM and Xerox, he joined Apple (AAPL) in the early 1990s and was a major advocate for putting CD-ROM drives into computers. (It seemed like a wild idea back when floppy disks ruled.)

Later at Sony (SNE), he helped establish the VAIO line. At Palm (PALM) he boosted the style quotient of the brand, and changed the naming system for the handheld computers. Roman numerals were out – names like “Palm 500” and “Palm 700” were in. (Chahil borrowed the naming system from luxury cars.)

Chahil also started working with a guy named Todd Bradley at Palm – and that relationship would bring him to HP. HP CEO Mark Hurd hired Bradley to lead a turnaround of the company’s PC business. And when Bradley needed someone to run marketing, he tapped Chahil. There he has led an image turnaround for the PC business, using his Hollywood connections and skillful handling of the press.

What’s next for Chahil?

For now I hear he’s helping to interview his replacements, and plans to step down at the end of the month. (Until the spot is filled permanently, one of his deputies, David Roman, will fill in.) For the next year he’ll serve as a consultant to the company. I also hear that he’s interested in spending more time on causes like education and healthcare, perhaps in his native India.

While I know those issues are close to his heart, I’m not sure I believe that’s all he’ll be doing. The guy’s always thinking about the next big idea – and with all the buzz about iPads and smartphones, it’s hard to imagine Chahil sitting it out for long.