If the Apple iPad explodes, and there's a pretty good chance it might, won't Windows-based netbooks be the collateral damage?To some extent, yes, although I'd still argue that netbooks and the iPad serve different purposes and different users.But because Windows (be it 7, Vista or XP) run on nearly all netbooks and regulation-size notebooks, Redmond could lose some market share if Steve Jobs' "magical and revolutionary" claims translate to astronomical iPad sales. Worldwide iPad sales are expected to amount to 7.1 million units in 2010, and nearly triple to 20.1 million in 2012, according market research firm iSuppli. That kind of volume should make Redmond skittish, although Microsoft's enterprise products like Windows 7 and Office 2010 should comfortably compensate for any netbook losses. Hewlett-Packard's Slate device.Another market researcher, DisplaySearch, forecasts in its "Quarterly Notebook PC Shipment and Forecast Report" that the tablet market, led by the iPad, will see significant growth this year and take market share away from netbooks. DisplaySearch predicts that consumers will pick up around 5 million tablets this year.The netbook appeal to buyers is still affordability (they now hover around $300) and are ideal as a second or third PC. But if tablets like the iPad and the upcoming HP Slate running Windows 7 catch fire with the general public, netbooks will inevitably start to fall by the wayside. There's not much Microsoft can do about this trend; netbooks were not designed to compete with tablet PCs. \nBut what Microsoft, and its OEM partners, need to do and can do is fully arm themselves for a tablet war if the iPad does start a revolution.While the iPad is predicted to be a netbook killer, you could just as easily argue that it will cut into MacBook and iPod Touch sales. If you're already an Apple fan(boy) and your iPod Touch has lost its luster (and you don't have the funds for a MacBook), there's a new option for you, in case you haven't heard. Reportedly, that's exactly who the early iPad adopters are so far: regular Mac and iPhone users. Of course, a lot depends on how the iPad is received by mainstream customers and PC users. If it ends up being a luxury device for Apple enthusiasts, Microsoft need not worry too much. But if iPads gain traction as a mass-market computing device, Windows netbooks and even low-cost notebooks (more comparable in price to the iPad) will become vulnerable. \nEither way, it's time for Windows-based tablets to come out of hiding.Which could explain the re-emergence of Hewlett-Packard's Slate tablet on Monday. HP released a video promoting the Slate along with a company blog post, as if to say: "Please don't forget about us."HP's Slate tablet was displayed by Steve Ballmer at CES in January and then hardly spoken of until now. The HP video emphasizes features in the Slate that the iPad lacks such as a Webcam, USB connections and Adobe Flash support. The message is clear: We want to compete with the iPad -- though an early leak of the HP Slate specs reveals that it lags behind the iPad in areas such as battery life and boot up times.Obviously, if the iPad becomes all the rage, Microsoft is not going to show up to that fight with netbooks but rather with an armada of Windows 7 tablets. The HP Slate looks to be the first, but it needs to be in customers' hands, like, a year ago. \nCorporate blog posts and promotional videos are meaningless when the iPad is already out there. And as anyone with a pulse knows, the iPad is really, really out there. What do you think? Where does the iPad threaten Microsoft the most and what should Microsoft do about it?Shane O'Neill is a senior writer at CIO.com. Follow him on Twitter at twitter.com\/smoneill. Follow everything from CIO.com on Twitter at twitter.com\/CIOonline.