Windows RT fails to make an impact in an exploding tablet market

Researchers at IDC said manufacturers shipped 200,000 tablets running Windows RT, the special version of Windows for iPad-style tablets, in the January to March period. That's down from about 900,000 shipped in the fourth quarter.

Microsoft Corp. launched Windows RT in October, along with the Surface tablet (Review). The software runs on a few tablets from other manufacturers as well. Windows RT is designed to run on phone-style chips, of the kind used in the iPad, rather than PC-style chips, which tend to use more energy and require bigger batteries. Using Windows RT means the tablets can be thinner and lighter, but it also means regular Windows programs won't run on Windows RT. That's caused some confusion and limited the appeal of Windows RT, analysts say.

Microsoft's larger Surface Pro tablets, which run standard Windows 8, did better in the quarter. IDC didn't specify how many, but it's at least 700,000 based on the figures provided.

Microsoft has said it plans to release a series of smaller tablets in coming months, apparently to compete with Apple's iPad Mini and Amazon.com Inc.'s Kindle Fire. Windows RT is the likely software choice for the tablets.

Meanwhile, the global tablet market more than doubled to 49.2 million units, according to IDC's estimate. That means nearly two tablets were sold for every three PCs, a record level.

Apple Inc. remained the largest maker of tablets, but its market share shrank to 39 percent, the lowest yet. Samsung Electronics Co. is cementing its position as the second-largest maker of tablets, with 18 percent market share, according to IDC.

Microsoft's market share was 1.8 percent, with 900,000 Windows RT and Windows 8 tablets shipped. It's at No. 5, behind AsusTek Computer Inc. and Amazon.