Microsoft warned investors today that PC shipments may have dropped below analyst estimates. Tami Reller, chief financial officer of Microsoft’s Windows division, revealed the news during an investor call on Tuesday. Bloomberg reports that analysts estimate total PC shipments fell around one percent in the latest quarter, likely due to the flooding in Thailand last year. A number of vendors have been hit by supply shortages for hard drives, resulting in longer lead times for PCs.

Microsoft's Windows sales have missed targets previously, and competition from Apple's strong iPad and MacBook Air sales has helped slow down shipments of traditional PCs. Microsoft is clearly banking on Windows 8, its latest operating system designed for touch, to help revive the PC market. The company's main sources of revenue, Office and Windows, is heavily invested in the health of PC shipments. Next week's Q2 2012 financial results, due on January 19th, will reveal if the Windows division is affected by weaker PC sales or not.