Worldwide PC shipments this quarter are projected to be down almost 8 percent from last year even after the launch of the highly touted Windows 10 operating system. This week, Intel, Microsoft, HP, Dell and Lenovo joined forces to launch an ad campaign, called “PC Does What!?” that they hope will help.

Worldwide, there are 500 million PCs that are five years old. So, competitors are getting together to try to sell you a new one. Olivier Toubia, professor at Columbia Business School, said this is a unique approach.

“It’s kind of surprising and unexpected to see competitors advertising together, which gets your attention,” he said.

But these companies are fighting for a sale. So shouldn’t they care who wins?

Daniel Ives, technology analyst at FBR Capital Markets, said the companies certainly want a piece of the pie, but this is about making the pie bigger.

“Which speaks to why they’ve had to go under such a groundswell-type of campaign and go arm and arm together,” he said.