More than five years after Microsoft (MSFT) released its last major PC operating system, the company on Thursday is finally rolling out a new version, Windows Vista, for corporate customers. The software giant is counting on new versions of its two cash cows — Windows and the Office productivity software suite — to boost sales and profit. On Thursday, Microsoft will also release to corporate users Office 2007, an upgrade to its popular suite that includes Word, Excel, PowerPoint and Outlook.