Tip: You can still buy a Windows 7 PC

• You can still order Windows 7 machines from HP, Dell and others
• Choices will be more limited than for new Windows 8 PCs
• Microsoft has not set a deadline for vendors to stop shipping Windows 7

Question: Do I have to get a new Windows computer with Windows 8? Can't I just order up one with Windows 7 instead?

Answer: Microsoft's new operating system brings more changes for existing users than any release since Windows 95 — its minimalist, touch-input-optimized Start screen; the absence of the Start menu; a new app store; a redone interface in the desktop's File Explorer windows.

But Windows 8 is not an inevitable part of your next computer. Hewlett-Packard and Dell, for example, not only continue to sell machines with Windows 7 preinstalled but prominently list that option on their sites; so does Best Buy. (Acer and Amazon, meanwhile, leave it to you to search individual listings.)

That doesn't mean you get the same selection, however. HP lists 16 Win 7 laptops against 60 Win 8 models. At Dell, it's 15 with the 2009-era Windows 7 and 57 with this year's release. Lenovo's site offers 11 ThinkPads with Win 7 and 47 with its replacement.

So if you were set on a particular price, weight, screen size or estimated battery life, those factors may close out your decision for you. Say you want a laptop with display smaller than 12 inches: At HP, the screens of Windows 7 computers don't go smaller than 14 inches, and at Dell the minimum is 13.3 inches.

Your selection may dwindle further over time, but Microsoft has not yet set a deadline for computer vendors to stop shipping Windows 7. One may not come for years: The Redmond, Wash., company didn't cut off manufacturers from selling PCs with Windows XP until October of 2010.

You could also try installing a separate copy Windows 7 on a new computer, but a legitimately-purchased edition will bulk up the price of a new computer that came Windows 8. And you may find that some of the machine's components go unrecognized by Win 7.

(One reader asked about installing Windows XP on a new computer. No, no, no: You'll probably run into far more hardware-support issues, and XP is dangerously insecure compared to Windows 8.)

On Tuesday, Microsoft said it had sold 40 million licenses of Windows 8 since its debut in late October. That number about matches Windows 7's first month in the market--but Win 7 upgrades cost a lot more, at $120 versus the $39.99 deal Microsoft is offering through January.

If the new interface of Windows 8 bothers you that much, it may be easier to paper it over with third-party software: Programs like the $5 Start8, noted here a few weeks ago, can recreate the Start menu and suppress the Start screen. You'll still have the security upgrades Microsoft added to this release; Win 8's performance improvements will also remain, although on a new computer Windows 7 would also seem faster than your old machine.

A month into spending my own $39.99 to put Windows 8 on a year-old ThinkPad, I'm still figuring some things out but overall don't mind the change. But I also spend the bulk of my time on that machine in a few core programs; your PC usage may not look much like mine.

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Tip: Windows 8 spells "backup" as "File History"

One of the less obvious changes in this release is a File History backup tool that, unlike Windows 7's, lets you recover individual files instead of entire backup sets and also remembers versions of files, allowing you to undo your own mistakes as well as recover from system crashes.

To turn on this new File History option, open the Control Panel — not the one in the new "charms bar" menu, but the traditional program you run in the desktop — and click "Save backup copies of your files with File History." Plug in an external drive or set up one elsewhere on your home network, then click the "Turn on" button.

From then on, the default settings will copy the contents of your user account's "libraries" (the Documents, Music, Pictures and Video folders), files on your desktop, your contacts and Internet Explorer favorites. And it will record any changes to them every hour.

Unfortunately, as other reviewers have noted, you can't add other files or folders to File History's routine. But — here's where things get a little weird — you can also use the older Windows 7 backup tool, which does offer that flexibility but doesn't allow rescuing individual files. In the File History window, click "Windows 7 File Recovery" in the bottom-left corner and, as before, connect an external drive.

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Rob Pegoraro is a tech writer based out of Washington, D.C. To submit a tech question, e-mail Rob at rob@robpegoraro.com. Follow him on Twitter at twitter.com/robpegoraro.