All eyes will be on Microsoft through the end of the year to see if Windows 8.1, the updated version of its maligned touch-based operating system, will be enough to repair the software company’s reputation and ignite interest in PCs and non-Android and Apple tablet sales.

The update became available to existing Windows 8 users yesterday morning as a free download. Microsoft will make paid-version available in the coming weeks.

Microsoft corrected the biggest compliant about the disconnect between tablet and PC users operating on the same platform. Business and power users complained that Windows 8 and its Modern (formerly Metro) interface was not conducive to traditional computing. Others complained that the dearth of applications and wonky interface wasn’t as clean as Android or Apple’s tablet interfaces. The universal complaint is the elimination of the Start button that allowed quick access to applications.

The Start button is returning in Windows 8.1, but doesn’t function as it does in previous version. Instead of providing a menu, it presents a page of available applications.

Windows 8.1 comes as PC sales in the U.S. are on the rise. Gartner recently reported that PC sales grew 3.5 percent in the last quarter as businesses started refreshing their fleets. Most businesses are still adopting Windows 7, the last version that still carries the traditional Windows look and feel.

Critics and analysts have pounded Windows 8 for failing to spark PC sales. While Microsoft says Windows 8 is selling well, PC manufacturers report no lift in sales since its launch. Overall PC sales are expected to fall as much as 9 percent in 2013.

Windows 8 also failed to build a beachhead for Microsoft in the tablet market. The operating system was designed to provide users the same experience in PCs and mobile devices. Prior to the launch of Windows 8, analysts predicted Microsoft would grow the total addressable tablet market by introducing an operating system that provide legacy connections to business applications and infrastructure. Thus far, though, users – consumer and business – have remain wedded to Apple and Android products.

Features, lack of applications and functionality haven’t been the only problems plaguing Windows 8. PC vendors have complained that that Microsoft is now a competitor with its device ambitions; the introduction of the Surface tablet is emblematic of the growing tension between Microsoft and companies such as Hewlett-Packard, Acer and Dell.

Solution providers, too, have relatively shunned Windows 8 because business customers prefer the look, feel and experience of Windows XP and Windows 7.

With Windows XP approaching its end of life in April 2014, businesses and consumers will have to make choices about operating systems. Upgrading will not be a choice. The arrival of Windows 8.1 will reveal whether Microsoft can still command the operating system market or if it will continue to struggle to find its way in the increasingly diversified computing world. The proof will come by year’s end as the market gears up for end-of-year business spending and consumer holiday buying.