I couldn’t find any columns on products you recommend for monitoring kids’ Web access and installing parental controls. I recently purchased a new computer for my 9-year-old daughter. I want to make sure she can only access specific Web sites and I want to protect her from inappropriate spam and chatting.

If you have a computer running one of the newer versions of Windows or the Macintosh operating system, I recommend using the extensive parental controls that are now built right into those operating systems. While you can never underestimate the ingenuity of computer-savvy kids, these built-in controls, if properly used, are generally harder to evade than the ones provided by third-party software.

I did recently review these built-in parental controls, which appear in Windows Vista, and in the Tiger and Leopard editions of the Mac’s OS X operating system. You can find that column at: ptech.allthingsd.com/20070614.

I want to switch to a Mac, but my life is on Microsoft Outlook, which is only available on Windows. Is there a simple way to convert all of this data to programs on the Mac?

There is a $10 program that performs this task. It’s called O2M (Outlook to Mac) and is from a company called Little Machines. It can be downloaded at littlemachines.com, where you also will find details about the Mac programs with which it works. This is a Windows program, which transfers your Outlook data into files you copy to your Mac. You then manually import these files into your Mac programs.

According to the company, the program exports Outlook email, email attachments, contacts and calendar appointments and allows you to import this data into Apple’s built-in email, address book and calendar programs, as well as into Microsoft Entourage, and other third-party programs.

Another approach is to install Windows on your Mac, and keep running Outlook. If you do this using the Parallels or Fusion virtualization programs ($80 each, plus the cost of Windows,) you can run Outlook simultaneously with your Mac programs.

Does the new version of Microsoft Office for the Mac work on pre-Intel Mac models?

Microsoft says it does, though I didn’t test it on one of these older machines. According to Microsoft, the new Office 2008 runs on any Mac “with an Intel, PowerPC G5, or PowerPC G4 (500 MHz or faster) processor.” However, you also need a relatively recent version of the Mac operating system, either the new Leopard edition, or the latest update (called 10.4.9) of the Tiger edition.

You can find Mossberg’s Mailbox, and my other columns, online for free at the new All Things Digital Web site, http://walt.allthingsd.com.

On two different new computers, I’ve created Word files and they’re automatically saved with the extension “.docx.” What is that? When I send these files via email, no one can open them. Can you shed some light?

In the 2007 version of Microsoft Office for Windows, which you appear to have on your two new PCs, Microsoft introduced new default file formats whose extensions end in the letter “x”. The one for Word is “docx,” for Excel it’s “xlsx” and for PowerPoint it’s “pptx.” You are using Word 2007, and all of your files are thus automatically being saved in the “docx” format.

Your correspondents can’t open these files because they are using older versions of Office that don’t recognize the new formats. Microsoft has made available a free auto-conversion patch for the older Windows Office versions, but most people don’t have this patch. (It can be found at microsoft.com/downloads under “Microsoft Office Compatibility Pack for Word, Excel, and PowerPoint 2007 File Formats.”)

There’s also a kludgy free stand-alone converter from Microsoft for the Mac versions of Word and PowerPoint, available at microsoft.com/mac under the name “Microsoft Office Open XML File Format Converter for Mac.”

Unless you can persuade all of your correspondents to install these workarounds, I suggest you change a setting in Word 2007 so that, henceforth, all of your files will be saved in the traditional “doc” format. That familiar format isn’t only compatible with older versions of Microsoft Office, but with many other programs, on both Windows and the Macintosh.

To make the change, first click on the round “Office Button” at the top left of Word 2007. Then, at the lower right of the window that appears, click on “Word Options.” In the next screen that comes up, click on “Save” in the column at the left. In the panel that appears at the right, you’ll notice an option called “Save Files in this format,” with a drop-down list of choices next to it. Display the list of choices by clicking on the arrow and select “Word 97-2003 Document (*.doc)”. Then, click OK at the bottom of the window.

Microsoft warns that some new features in Word 2007 won’t translate into the old format, but I believe that this will prove irrelevant in 99% of cases and is outweighed in any case by the incompatibility you have run into.

How can I transfer all my Outlook contacts from a Windows PC to a Macintosh contacts program?

There are a number of methods. You can use a PDA or smart phone that can synchronize the contacts with a Mac, after having first synchronized with Outlook on your PC. Or you can use a $10 program called O2M, which is specifically designed to move Outlook data to a variety of Mac programs. It can be downloaded at littlemachines.com.

Or you could get Apple to do it. The company offers a basic file transfer for free if you buy the Mac from an Apple retail store. But, if you want Apple to move Outlook contacts in just the way you want, you may have to purchase the company’s $99 a year ProCare service, which comes with a more complete transfer service.

I recently replaced an old Windows XP computer that was running very slowly. I want to continue to use it as the computer for our young kids, and I was thinking that if I format the hard drive and reinstall XP (which I bought to upgrade the machine a while back), it will probably improve its performance. Do you agree? And, can I reinstall my copy of XP, when I have already “activated” the software when I originally installed it?

I do agree that the computer will likely run faster after you wipe the hard drive and reinstall Windows. That is the usual outcome. And it should be possible to use it legally, as long as you haven’t made any major changes to the hardware, since Microsoft’s activation system typically allows Windows to be reinstalled on the same machine. If activation fails, you can call Microsoft and explain that it’s the same machine, and the company says it will usually OK activation in such cases.

You can find Mossberg’s Mailbox, and my other columns, online for free at the new All Things Digital Web site, http://walt.allthingsd.com.

Write to Walter S. Mossberg at mossberg@wsj.com

Here are a few questions about computers I’ve received recently from people like you, and my answers. I have edited and restated the questions a bit, for readability. This week my mailbox contained questions about breaking MP3s into separate tracks, wireless mice and transferring emails to Microsoft’s Entourage from a PC.

I’m downloading some lectures in MP3 format and then transferring each to an audio CD to listen to while driving. An occasional lecture in the series is too large to transfer to CD. Is there a program that will divide these into two tracks so that they can be written to separate CDs?

Yes, there are multiple little utility programs that can split (or join) MP3 files. I haven’t tested any of them, so I can’t recommend one. But you can find them by going to www.download.com and typing in “mp3 splitter.”

I am in the market for a wireless mouse for my Dell notebook. Do they perform well? Do you recommend a particular one?

Cordless mice do perform well, in my experience, and are now quite common. The only downside is that you have to replace their batteries occasionally, or remember to place them in a charger, if they use one. For laptops, especially on the road, Logitech and Microsoft make cordless mice, which are smaller than typical desktop models. But you should go to a store and actually try some out, to see which size and feel you prefer.

How can I transfer my Microsoft Outlook contacts and email from my Dell into Microsoft’s Entourage program on my new MacBook Pro? Entourage, which is supposed to be Outlook’s equivalent for the Mac, doesn’t seem to recognize my Outlook files. Shouldn’t a Microsoft email program recognize files from another Microsoft email program?

Yes, it absolutely should. It amazes me that Microsoft Office for the Mac includes compatible versions of Word, Excel and PowerPoint, but not Outlook. And it is truly annoying that Microsoft’s Outlook substitute for the Mac, Entourage, has no built-in way to recognize or automatically convert Outlook files from Windows.

Luckily, there’s a $10 third-party program that can do the conversion. It’s called O2M, from a company called Little Machines, and can be found at www.littlemachines.com. It turns your Outlook data into files that can be imported into Entourage, or into the Mac’s built-in email, address book, and calendar programs.

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Because of the volume of email I receive, I can’t routinely answer individual questions by email, or consult on individual problems or purchasing decisions. I read all questions I receive and select three each week to answer in the column.

Write to Walter S. Mossberg at mossberg@wsj.com