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Later this week, Windows users will have a chance to fix what's broken or break what's working.
But they may not know which path they chose until after they have installed Windows 7.
The latest Microsoft operating system, which is due on October 22, will replace Windows Vista, and that alone should be good.
My tests confirm that 7 uses less memory than Vista, makes it easier to manage open programs and windows, and throws up fewer "User Account Control" nags.
At the same time, Windows 7 will not put Mac OS X or Linux out of business.
Program installation and uninstallation remains as tedious as ever.
Old programs may not work in 7, and this new system strips out Windows components such as Microsoft's email software, the address book and the calendar.
Choosing whether to upgrade from Vista or XP, however, involves much more than 7's features and flaws.
The simplest scenario applies if you bought a copy of Vista or a new, brand-name computer from June 26 onward.
Under Microsoft's Windows 7 upgrade option, you will only pay, at most, shipping and handling for an upgrade edition.
And any new PC should easily exceed 7's system requirements: a 1 gigahertz or faster processor, 1 gigabyte of memory (double that if you run a 64-bit release of Windows), 16GB of disk space (again, double for 64-bit Windows) and a "DirectX 9 graphics device with WDDM 1.0 or higher driver" (needed for the optional Aero version of 7's interface, with its transparent visual effects).
But you should run Microsoft's free Upgrade Adviser program to check for any complications.
On the three Vista laptops I reviewed, Upgrade Adviser warned that a HP Pavilion fingerprint reader would need new driver software, while a Dell program-launcher utility and copies of Norton Internet Security on the HP and a Toshiba Satellite would have "minor issues."
Upgrade Adviser also noted that 7 would remove Vista's Windows Mail and parental controls, and suggested downloading Microsoft's free replacements (download.live.com).
Duly warned, I began installing Windows 7's release candidate on the Toshiba.
And about an hour and 45 minutes later, the laptop showed zero signs of distress to its hardware or software.
On older Vista machines, the upgrade process should remain the same, with one major exception: if you bought a computer with the overpriced Ultimate edition of Vista, you will have to do what Microsoft calls a "custom install."
"Destructive install" is more like it.
The Windows 7 installer clears out your files, settings and applications before putting a clean copy of 7 on the machine.
You can use Microsoft's Easy Transfer program to back up and restore your data, but there is no guarantee that it will put all of your files back in the right place - and it will not preserve your applications.
Things can be even worse with an upgrade from Windows XP to 7.
Microsoft even suggests hiring "your local computer service provider" for this move.
Why Microsoft might offer that advice became more obvious after an XP-to-7 upgrade on a battered, five-year-old Dell laptop.
The Easy Transfer program on the Win 7 DVD worked well enough - within minutes, it had located my data, including settings for such non-Microsoft applications as Mozilla Firefox and Apple's iTunes, saved to a USB flash drive.
The custom installation also went by quickly, finishing in about 45 minutes.
But when this Dell booted up into Windows 7, its sound and ethernet network port no longer worked, and its screen had been set to a too-low, blurry resolution.
I fixed the screen easily enough, and a troubleshooting tool in 7 found a driver at Dell's site that got the audio working.
But it offered no simple fix for the ethernet.
Restoring my old data with Easy Transfer revealed other problems.
Firefox bookmarks and settings had returned, but iTunes did not find my songs or playlists. (That could be an iTunes bug, as the MP3 files were in the right music folder.)Windows XP users can avoid a custom install by buying a copy of Vista now, doing an in-place upgrade with that and then getting a free copy of 7 through Microsoft's Upgrade Option.
But that is a lot of time spent installing Windows.
With all of these upgrade scenarios, there is another issue.
Every time I've tried a new Windows release - even one of Microsoft's free Service Pack patches - I've heard from a small but angry minority of readers complaining that the upgrade had sunk their system in one gruesome way or another.
There's nothing in Windows 7 to suggest it would be free from this phenomenon.
So after you have checked your PC's hardware and software, you may want to ask one other question before committing to a Windows 7 upgrade.
Do you feel lucky?
Microsoft's new Windows 7 operating system sports several new consumer-friendly features.
Here are our three favourites: Search At long last, Windows gets a decent search function to speedily track down words or phrases on stored documents or other files.
Snap This handy feature enables a user to position two files side by side and then easily copy and paste from one to the other.
You could have your notes on the left side of the screen, for example, and the great American novel you're writing on the right.
Taskbar The icons of programs are lined up along an edge of the screen in a much-improved taskbar.
Place your cursor over an icon and you get thumbnail views of all the program's open windows, no matter how far they're buried under other stuff on the screen.