Microsoft is retooling the latest version of its Windows operating system to address the complaints and confusion that have been blamed for deepening a slump in personal computer sales.The tune up announced yesterday won't be released to consumers and businesses until later this year. The changes, part of a software package given the code name "Blue”, are meant to fix perceived shortcomings in Windows 8, a radical overhaul of Microsoft Corp's ubiquitous operating system released last October.With the make over, Microsoft hoped to play a more prominent role in the growing mobile device market while still maintaining its dominance in PCs. But Windows 8's design, which emphasises interactive tiles and touch controls, seems to have befuddled as many people as it has impressed. One leading research firm, International Data Corp, says Windows 8 contributed to a 14 percent decline in worldwide PC sales during the first three months of the year — the biggest year-over-year drop ever.Despite the troubling signs, Microsoft insists it's pleased with Windows 8's performance.The company, which is based in Redmond, Washington, says more than 100 million Windows 8 licenses have been sold so far, up from about 60 million licenses in January. The licensing volume "is in the same general ballpark”, as Microsoft's previous operating system — Windows 7 — at a similar juncture of its sales cycle, according to Tami Reller, who serves as the marketing and financial chief for Microsoft's Windows business.In an interview, Reller said Microsoft still realised changes need to be made to make Windows 8 easier to navigate and capable of taking full advantage of technology improvements that have come out since October."Are there things that we can do to improve the experience? Absolutely," Reller said "There is a learning curve (to Windows 8) and we can work to address that."For now, Microsoft isn't saying what kind of changes will be introduced with the release of Blue, which the company plans to anoint with a different name when the update is available. Microsoft also isn't saying whether it will charge existing owners of Windows 8 devices to get the fixes in Blue. The company plans to release Blue in time for the holiday season.