At the Computer Electronics Show this week in Las Vegas, Microsoft has an opportunity to start the year off right and curtail the negativity that has been nipping at the software giant.That's a lot to ask of one show given how much negativity is hurled at Microsoft, but it's the biggest show around and Microsoft CEO Steve Ballmer has the keynote again. Here he can finally lay out Microsoft's roadmap for tablet PCs and explain how Windows (both 7 and the pending 8) will run on them.\n\n \n \n \n \n \n\n \nDuring last year's CES's keynote, Ballmer briefly displayed some "slates" running Windows 7, and then spent the rest of 2010 more or less avoiding the subject.That obviously can't happen this year, not with Apple's iPad quick rise to dominance in the nascent tablet PC market, which is starting to spill over from the consumer space into enterprises. Apple hasn't released holiday season iPad sales numbers yet, but market researchers forecast between 8 and 9 million in iPad sales for 2010 and more than double that for 2011.So Microsoft has some explaining to do and an ideal forum in which to do it. So what is Ballmer likely to cover in his keynote address?Windows and ARM-based Chips. Together at Last?The Wall Street Journal reported just before Christmas that Microsoft will demo a slimmed-down or new version of Windows at CES for tablets that supports ARM-based processors. Incidentally, in mid-December, the New York Times reported that Microsoft will also debut Windows 7 tablets from Dell, Samsung and others at CES, citing unnamed sources.So the Microsoft tablet picture is coming into focus, albeit at a glacial pace. Making Windows more available on ARM chips makes sense for Microsoft. Chips based on the ARM design use less power than Intel's x86 chips, which Microsoft has long used in Windows-based desktops, laptops and netbooks. ARM-based chips are the preferred chip for tablet PCs and smartphones, including the iPad and the iPhone, the BlackBerry and Windows Phones.Ballmer needs to address how quickly ARM-based Windows 7 tablets will be available and give us a look at the UI and reveal specs such as battery life (10 hours, please). But the bottom line is there will be an ARM version of Windows, a necessary step for Microsoft. Whether Microsoft can slim down Windows 7 to work well on the tablet form factor or apply Windows Embedded Compact or even the Windows Phone 7 OS, Ballmer needs to convince us that his troops will move fast on tablets in 2011. Or else.A Glimpse at Windows 8?The Wall Street Journal story also reported that Microsoft will demo an early version of Windows 8 at CES.There are pros and cons to opening the Windows 8 kimono. Yes, it will be exciting to catch a glimpse of the future Windows UI on a tablet, and Windows 8 will definitely be more touch- and tablet-friendly than Windows 7. But Windows 8 will not be available realistically until 2012, so Ballmer should be careful not to oversell it and create a "hurry up and wait" situation.Meanwhile, he needs to convince the audience that a slimmed-down version of Windows 7, which was not designed to work easily as a touch-based tablet interface, can get the job done on tablets now. Clearly, waiting a year and a half for Windows 8 is not the tablet solution for Microsoft.Whatever hardware and version of Windows Microsoft reveals at CES this week, it's definitely tablet time. That will be the overarching theme, and it's a big chance for aggressive marketing and clarity on Microsoft's current Achilles' heel. Expect Ballmer and company to come out with all tabs blazing.Shane O'Neill covers Microsoft, Windows, Operating Systems, Productivity Apps and Online Services for CIO.com. Follow Shane on Twitter @smoneill. Follow everything from CIO.com on Twitter @CIOonline. Email Shane at email@example.com.