This has been a pretty bad news week for Microsoft and we should probably expect a lot more of them going forward. Barron’s points us to a new note from Merrill Lynch software analyst Kash Rangan, who thinks that PC sales haven’t come close to bottoming out yet. In fact, Rangan estimates that “if roughly 50% of consumer PCs (20-25% of total) represent low-end devices which are at risk of cannibalization by tablets, then PC units need to decline by 20-25% to get to trough growth.” While this will certainly be a trying time for Microsoft and its OEM partners, Ragnan sees things stabilizing after consumers are through switching out tablets for new PCs because Microsoft still has a “stable and nicely growing enterprise business.”