Microsoft (MS), Sony and Intel all announced new layoffs this week, providing confirmation of industry observer’s predictions that the tech sector economic slump is still far from bottoming out.

Microsoft led off with an announcement that shocked many in the tech sector: Q4 2008 financial results were so disappointing that the company felt compelled to lay off at least 5,000 employees to shave costs, the first company-wide layoffs in MS’s history. Some 1,400 jobs were terminated immediately with the remainder scheduled to disappear over the next 18 months.

ZDNet published a copy of the e-mail message MS CEO Steve Ballmer sent all employees explaining the layoffs and associated cutbacks.

Simply put, MS sold far fewer copies of its flagship Windows operating system than it hoped to because there were far fewer new computers than usual sold in the usually busy holiday quarter.

Intel is also suffering from weak sales of personal computers, for which Intel is the leading supplier of microprocessor (brain) chips. As a result, the company is laying off 6,000 workers and closing four chip fabrication plants in Malaysia, the Philippines and the U.S.

Meanwhile, Intel’s arch competitor in the processor market, Advanced Micro Devices (AMD) posted its fourth consecutive quarterly loss for a total fiscal 2008 loss of just over (US)$3 billion. But AMD isn’t talking layoffs or plant closures – at least, not yet.

And Sony, which already announced a major restructuring initiative late last year involving layoffs that could total 16,000 worldwide, this week announced the closing of two more plants resulting in 2,000 more layoffs. The company finished 2008 in even worse shape than it first feared, predicting a (US)2.9 billion loss for 2009, its first annual loss in 14 years.

Sony’s problems stem, in large part, from tanking sales of the high-end consumer electronic gadgets in which is specializes, notably, big-screen televisions.