For quite a few years MSFT has had strong competition from linux, especially in Europe. Linux is an outstanding OS, but the less expensive and free versions have not been very user friendly, not friendly enough to deal a knock out blow to MSFT. A Microsoft advantage over Linux is that there are some very popular software packages, e.g., Turbo Tax, Quicken, and a number of other popular programs, that do not have a Linux version and the Windows emulators that run on Linux, e.g. Wine, do not run a lot of this MSFT specific software well. Microsoft is living on borrowed time, however, because eventually someone will produce software equivalent to Turbo Tax and Quicken and a few other critical programs that runs beautifully on Linux and seemlessly imports old files created under the Microsoft OS. When that happens there will be very few reasons, if any, to stick with microsoft. Microsoft has produced one, and only one, very good OS so far, and that is XP. Possibly Windows 7 will also be good, Vista and most of the other operating sytems they have sold are disasters. I believe we would not have even gotten XP had it not been for competiton from Linux.
