Earlier quoted context omitted.
Actually, their substantial diversification beyond Windows means that it's very, very unlikely Microsoft is going to fall (easily or quickly). Microsoft could lose the entire consumer Windows business and be just fine (despite the hit their stock would take), particularly as they keep growing in other sectors while Windows becomes less important by the day (and is clearly done growing as a business). Consumer Windows…
The vast majority of Microsoft's profits come from Office. Windows makes a little bit, and everything else loses money.
Operating Income by Division FY13 Q3: Windows: $3.46 B Server and Tools: $1.98 B Online Services: -$262 M (loss) Business: $4.1 B Entertainment and Devices: $342 M
It is interesting that people perceive so many businesses at Microsoft as "failing" even when they have healthy income and growth year after year.
Source: http://www.microsoft.com/investor/EarningsAndFinancials/Earn...