In a historically un-Microsoft move, Microsoft has been considering ad-supported versions of popular Microsoft software such as Office and Windows. This is apparently their answer to the increasingly backlash over the high price of MS software. So now, instead of popups plaguing you when you browse, you now have popups built into the software itself! That can't be all peaches, as Microsoft has admitted:

"It seems possible that we could match that revenue via ads, but there are difficult UI (user interface) issues to solve, since the OS does not have a natural way to display ads that does not annoy users,"
Some people think the idea is complete rubbish, yet others say it's a fine way to get Windows into the hands of those unwilling to pay the steep price, or offer Microsoft alternatives.