Reason 1: i do alot multimedia stuffs on windows, Gimp is good, but it's not photoshop, plus, as multimedia editing goes, Gimp is about as far as Linux gets.
Raeson 2: i also do alot gaming on linux, halflife 2, counter strike source, etc...
duel to those two main reason, i m stuck with windows....*sigh*...
50% of my computer usage is taken by those 2 reasons mentioned above, 30% web browsing (including blogging, etc etc...) 20% other random stuffs (watch video, listen to mp3, etc etc...)
linux can only fufill 50% of my needs, while windows gives me 100%, I love linux, and i have couple linux set up as my 3D randering farm, and a laptop with kubunto, but as for daliy usage, a windows box fits my needs better.( still hate windows tho....)
Mac OSX is nice....but not too sure about the hardware....I have mac osx x86 running on another laptop just for fun....but it's slooooooww... ><