Unlike in baseball, when it comes to operating systems, it's two strikes and you're out. Given that Microsoft missed with Vista, if Windows 7 isn't a big hit, Microsoft is in for serious trouble.

Vista was as close as a disaster as it gets for Microsoft. It wasn't just the bad publicity that was the problem --- people stayed away in droves. And that had a big impact on the bottom line. In April, Microsoft reported its first quarterly loss ever, and although the general economy was the cause, problems with Vista didn't help. The biggest losses were from the division in charge of operating systems. If Vista had been a success, it's not clear whether the losses would have been as big.

The last time Microsoft had an operating system that bombed was back in 2000, with the dismal Windows Me, which was the buggiest, most ill-conceived operating system the company ever released. But it was only a year until the next version of Windows, XP, so the ill effects were short lived.

With Vista, by way of contrast, it will be close to three years before its successor Windows 7 is released. So Microsoft has had to endure three years of criticism, with Windows becoming an increasingly tarnished brand. So there's a lot riding on the success of Windows 7.

Making matters worse is that it's not clear how important operating systems will continue to be. With Web-based applications and the cloud becoming increasingly dominant, the browser is slowly becoming what the operating system used to be. Microsoft needs to prove that there's a reason to care about what operating system you use, and offer a reason to use its operating system. It also needs to show that it can create compelling software, so that when the cloud-based future arrives, people will be willing to give Microsoft's offerings a try.

In addition, Microsoft needs to convince system makers that they should include Windows 7 on their hardware, rather than Linux, or in the future, Chrome. If system makers see people turn down Windows 7 in the same way they turned down Vista, they'll be more open to selling hardware with other operating systems on it.

That's why Windows 7 may be the most important operating system launch in Microsoft's history. It can't afford another miss like Vista.