Of course, I'm not exactly a large corporation. I'm just another one of the 200 million or so PC users who are using operating systems Microsoft no longer supports. In September 2004, according to IDC, of the 390 million PCs running Windows around the world, Windows XP Pro runs on 26.1% and Windows XP Home on 24.7%. Total: 50.8%.
Those numbers have changed with PC sales since, but that still means probably something like 40% of Microsoft customers are running Windows 2000, Millennium, 98, 95, or earlier. (I've got one earlier--a museum-quality Compaq notebook, 16-line screen, CGA graphics, and Windows 3--yes, there were CGA drivers for Windows 3.)
Microsoft's problem is that it made its bed in browsers, and now we have to lie in it. The company used its tremendous power over the market to set the price of the Web browser. And it set it at zero. Remember when the browser was so important it had to be part of the operating system? That probably seemed like a good idea in Redmond at the time--it strangled Netscape in its crib, which was evidently the goal. But it also cut Microsoft off from a revenue stream that now I'll bet it wished it had.
Today the browser is still free, and it's still part of the operating system, and Microsoft is still insisting that the only way to upgrade to a safer, more secure version of IE is to upgrade to Windows XP Service Pack 2, the only version of Windows still supported by Microsoft.
(Has it occurred to anybody else that if the ship date of Vista were to slip yet again as badly as it has in the past and Microsoft stuck to its announced sunset date for XP support, we might actually live in an era when Microsoft would support no version of Windows?)
Of course, Microsoft has repeatedly denied that it intends in any way to profit from the security issues with its products, but the fact remains that every action it takes makes upgrades more inevitable, rather than less. And on terms more favorable to Microsoft and less favorable to its customers.
So what are almost half the Windows users of the world supposed to do about a more secure browser? Microsoft's answer seems to be, "Let them run Firefox."