I can't answer this because I really have no idea. I wonder if everyone is seeing an overall drop because the end user has so many options available to them these days and the market seems so diluted with new products daily that the pieces of the pie have gotten smaller overall.

I am not an expert either but I think its market saturation and lack of any major OS release, PC market tends to increase when there is a new Windows release as most people are hoodwinked into upgrading their existing PC to a new one.

Apple has also rebound in the PC market, to apple's rebound will contribute to the downward turn for other PC manufacturer.