Vendors must find ways to persuade end-users to replace their PCs more frequently, ... Dataquest believes that the new generation of small form-factor PCs will be instrumental in making this happen.
This bump in sales in the market is due to PCs that were bought around the Y2K time frame. That's certainly slowing down.
Notebook computers now offer much of the functionality of desktops, and consumers and businesses alike are spending the extra for the added benefit of mobility. In that sense, mobile growth is coming at the expense of desk-based PCs to some extent.