Microsoft shares were hammered Friday after a disappointing earnings report cast doubts on the tech giant\'s transition to a post-PC world. Shares in the US tech giant plunged 11.4 percent to close at $31.40. The company announced a profit of $4.97 billion in the past quarter, but its results were hit by a writedown linked to disappointing sales of its Surface tablet computer. \"These results demonstrate that the weak PC market is clearly catching up to Microsoft and the recently announced restructuring will take time to positively impact the business and seems limited from a cost saving perspective,\" said Barclays analyst Raimo Lenschow. Microsoft took a $900 million charge for \"inventory adjustments\" for its Surface RT, the device aimed at breaking into the tablet market, which is growing while traditional PC sales are slumping. Microsoft has not released sales data for Surface, but analysts say the device has been disappointing. Microsoft said that consumer PC sales were down 20 percent from a year ago, but are trying to transition the company to mobile computing. \"Our Windows business declined as the device market continued to evolve beyond the traditional PC,\" Microsoft Chief Financial Officer Amy Hood told analysts Thursday. \"We are working to transition the business into this modern era of computing, taking advantage of the new scenarios enabled by Windows 8,\" she said. \"As we\'ve said before, given the complexity of the ecosystem, this journey will take time, but we continue to make incremental progress.\" Microsoft last week announced a sweeping reorganization of the company to \"enable us to innovate with greater speed, efficiency and capability in a fast changing world.\" The \"far-reaching realignment\" was designed to help integrate efforts around its software and devices. But many analysts remained skeptical. \"PC sales will likely remain a headwind for the foreseeable future,\" said Matthew Hedberg at RBC Capital Markets, who cited a \"lack of near-term catalysts\" and \"limited demand thus far\" for its Surface tablets. Ross MacMillan at Jefferies said that the new Windows 8 operating system \"is an attempt to create a single OS for PCs, tablets and hybrid devices,\" but that \"initial reviews suggest a steep learning curve and expectations for the product cycle are low.\"