Microsoft Corp.'s (MSFT) long-awaited Windows 8 operating system will go on sale Oct. 26, its most critical software upgrade in a decade. Designed to work on both PCs and tablet computers, Windows 8 is Microsoft's best hope for competing with devices running Google Inc.'s (GOOG) Android operating system and Apple Inc.'s (AAPL) iPad. The Redmond, Wash., company made the announcement in a blog post late Wednesday after Steven Sinofsky, head of Microsoft's Windows team, announced the date at the company's annual sales meeting. Windows powers nearly a billion PCs world-wide. To sustain sales of its Windows 7 operating system through October, the company has said buyers of selected versions of Windows 7 through the end of January 2013 will be able to upgrade to a version of Windows 8 Pro at a discount. Accounting for the promotion will force Microsoft to shift between $450 million and $550 million in revenue to future quarters from the current quarter. The accounting move won't affect cash flow, but shifting that revenue to future quarters will diminish per-share earnings by about five cents in the quarter ended in June. Microsoft will release those earnings at the close of the market Thursday. Write to Steven D. Jones at steve-d.jones@dowjones.com Subscribe to WSJ: http://online.wsj.com?mod=djnwires Subscribe to WSJ: http://online.wsj.com?mod=djnwires
