Oct. 18--On Thursday, Microsoft will start selling the latest version of its flagship Windows operating system. Gone are the days when people lined up days in advance to update their PC's software, but the release of Windows 7 remains a big deal.

Certainly, it matters to Microsoft. The company is still smarting from the mistakes it made with Windows Vista, which has earned such negative buzz that it now ranks right up there with Windows ME as one of Microsoft's most embarrassing products. Microsoft is counting on Windows 7 to get its mojo back.

Of course, the bottom line is: What will it do for you? If you're a Windows XP or Vista user, should you upgrade your home or small-business computer?

I've been working with unfinished versions of Windows 7 for months, and with the final version since it was completed in August. I like it, but how happy you'll be depends on what you do with a computer and what operating system and software you're using now.

I asked the readers of my TechBlog to suggest some questions I might answer in a review of Windows 7. I've also been keeping track of queries that came via e-mail and on Twitter. With that in mind, this review takes the form of a Frequently Asked Questions document, or FAQ.

Q: How much will it cost to upgrade to Windows 7? And which edition should I buy?

A: The cost of upgrading depends on two factors: which of the three retail editions you choose and what you may need to do to upgrade your PC.

At the very least, upgrading an existing system to Windows 7 will cost about $120 -- the list price for the upgrade version of Home Premium, the edition that will be fine for most home users. There's also the Business Edition, with features designed for professional users and lacking some consumer options -- there's no Media Center in Business, for example, which lets you watch TV and movies on your PC. The Ultimate edition, for $220, contains the features in both Home Premium and Business. You can find a comparison of the three editions at www.windows7.com.

The system requirements for the version of Windows 7 for 32-bit processors calls for a 1-GHz processor and 1 gigabyte of RAM; the 64-bit version needs the same processors and 2 GB of RAM. Frankly, I'd recommend 2 GB for both systems. Additional memory is cheap and easy to install in desktops and many notebooks. Expect to pay around $50 for 2 GB.

Q: Windows Vista's interface changes seemed like mostly eye candy. How is Windows 7 different?

A: Both Vista and Windows 7 sport a slick look Microsoft calls Aero.