With software it's really hard to say what below cost actually is. Amortized fixed cost, or just the variable cost? If you are talking about the latter then no

With software it's really hard to say what below cost actually is. Amortized fixed cost, or just the variable cost? If you are talking about the latter then no, it's probably not dumping. If you are looking at the former I bet it's not so clear cut. WinXP development and all of the associated cost (such as the loss-making products like IE that help keep WinXP in it's market position) would have been pretty expensive - and the expenditure is still going on today thanks to things like security support and IE upgrades.