Windows 7 has arrived. After three years of development and testing, Microsoft is releasing the new operating system to the world Thursday with a full slate of festivities in New York and a remote ringing of the NASDAQ opening bell from the company's Redmond headquarters.

But the most interesting stuff will happen in homes around the globe, as people upgrade existing computers and boot up newly purchased PCs preloaded with Windows 7. If you plan to be one of those people, here's a guide to a bunch of online resources that should help.

WINDOWS 7 FEATURES: The uninitiated can get a quick sense for what Windows 7 can and can't do through reviews -- such as those published by CNet, the Wall Street Journal, the Washington Post, and USA Today. Read the glowing remarks with a grain of salt, however, because positive reviews don't necessarily translate into winning products -- as demonstrated by Windows Vista.

Also see our informal survey of Windows gurus for more on the pros and cons of the new operating system. Microsoft's official site offers descriptions and videos of many key Windows 7 features. And of course, there are already plenty of Windows 7 books available, as well, if you're interested in even more information.

SHOULD YOU UPGRADE? Maybe, maybe not. "If you have an existing machine, and you have Windows XP or Vista on it, don't feel overly pressured to go get Windows 7," said Jon Bach, president of Seattle-area custom computer builder Puget Systems, during our recent visit to his shop. "But if you're getting a new machine, yeah, I don't see any reason not to go with the latest and greatest."

If you decide to go for a new machine, you just might land yourself a deal. Microsoft and its industry partners are rolling out a series of special offers on new computers in the coming days -- starting with Best Buy's package of three computers, and more, for a total of $1,200. Watch the Windows home page for more.

SYSTEM REQUIREMENTS: This Microsoft page lists the minimum specs your computer will need to run Windows 7 -- including a 1 GHz processor and 1GB of memory. In some cases, however, experts suggest exceeding those minimums significantly for an optimal experience. Bach, for example, recommends 4GB of memory.

Also check out Microsoft's Windows 7 Upgrade Advisor, which scans a computer to see if it can run the new operating system. In addition, the Windows 7 Compatibility Center provides a sense for whether your devices and peripherals will work with Windows 7.

ALTERNATIVES: Of course, there's more to computing than Windows. Apple and IBM hope to persuade consumers and businesses to switch to Mac or Linux rather than moving to Microsoft's new version.

DECIPHERING WINDOWS 7 EDITIONS: The complexities of Microsoft's Windows product lineup remain a frequent target of criticism. This Microsoft page compares the many Windows 7 editions. As a rule of thumb, however, Microsoft says most consumers should go for Windows 7 Home Premium ($119.99 to upgrade from XP or Vista; $199.99 regular price) and most businesses should pick Windows 7 Professional ($199.99 upgrade; $299.99 regular price).

SOFTWARE DISCOUNTS: For college students, the cheapest route is to take advantage of this promotion in which Microsoft is offering Windows 7 for $30. And people planning to upgrade multiple Windows PCs should take a look at the Windows 7 Family Pack, which lets PC users upgrade to Windows 7 Home Premium on up to three existing Windows Vista or XP computers for $149.99. That's more than $200 less than buying the upgrades individually.

UPGRADING FROM WINDOWS XP: Many people are still using Windows XP PCs. The good news is that Windows 7, unlike Windows Vista, has been fine-tuned to help it run on many older machines from the earlier Windows XP era. I've been running Windows 7 smoothly on an older IBM ThinkPad that originally came with Windows XP.

The bad news is that an upgrade on a Windows XP computer can be a pain in the butt, requiring users to back up their data and applications and make a fresh installation of Windows 7, then reinstall the data and applications after the new operating system is in place. Windows Vista users, in contrast, will be able to make an "in-place" upgrade, shifting to Windows 7 while preserving data and programs.

See our earlier post for more details: "Leaping from Windows XP to 7? Some important stuff to consider." If you're willing to spend some money to smooth the transition, Bellevue-based Laplink Software is offering its PCmover software and related tools to help people make the shift from Windows XP to Windows 7.

Do you have more questions about Windows 7? Email them to us here or submit them in the comments below, and we'll try to address them as soon as we can in updates to this post.