A: You will begin to see more touch-screen laptops after Oct. 22, when Windows 7 comes out, because that new operating system has optional fingertip touch-screen navigation built in. In addition, many of the major Windows PC makers are adding their own touch-navigation systems to newer models.

However, I’d offer two caveats. First, not every touch screen will be capable of performing all the multitouch actions and gestures Windows 7 will offer. Some are more limited in their capabilities.

Second, the hardware makers will likely be cautious at first about adding fully capable touch screens to all or most of their laptops.

This is partly because these screens can add significant cost in a price-conscious market, and partly because nobody is certain how popular touch-screen navigation will be on laptops as opposed to, say, on all-in-one desktops where reaching for the screen is more obvious and natural.

I have an Apple iMac, and an Apple iPhone with around 122 apps. My question is, why don’t these iPhone apps work on the iMac? Both units use the same operating system, so why not?

A: While the iPhone and the iMac each use a version of the same operating system, Apple’s OS X, they aren’t the same operating systems. The version on the iPhone is stripped down, and has been modified to support an entirely different user interface, navigation system and set of hardware capabilities.

So there are two separate collections of apps, or programs, that run on the two platforms.

I am currently running Windows Vista Ultimate on my Dell PC. I have regretted it ever since I upgraded from XP because of its terribly slow performance. I have heard good things about Windows 7 but I am afraid I will have to buy the more expensive Ultimate upgrade (which I don’t really need) instead of an upgrade to Home Premium or Professional. Is that true?

A: According to Microsoft, owners of Vista Ultimate can only perform an “in-place upgrade” to Windows 7 Ultimate, not to lesser versions. An “in-place upgrade” is the type most people think of, the type where all your programs and files and settings are preserved just as they were, but you emerge with the new operating system.

Even then, you must be careful to buy the edition of Ultimate that matches the type of architecture your machine possesses, either 32-bit or 64-bit.

However, you can downgrade to the Home Premium or Professional versions of Windows 7, if you are willing to do a lot more work, by opting for what Microsoft calls a “custom installation,” something commonly known as a “clean install.” This typically means, first, backing up all your files and settings to an external hard disk, then allowing the Windows 7 installation disk to wipe your hard disk clean before installing your preferred version of Windows 7.

You would then copy back all your files. But you cannot do the same with your programs. For these, you would have to reinstall every one, from their original disks or downloaded installation files, and then download and re-install all the patches and program upgrades that have been issued by their makers since you acquired them.

You can find Mossberg’s Mailbox, and my other columns, online for free at the All Things Digital Web site,

http://walt.allthingsd.com.

When will Google offer its much-discussed cellphone for sale?

Google says it isn’t planning to build or sell mobile phones. Instead, it is developing a cellphone operating system, or software platform, called Android. And it has assembled an alliance of companies, including phone makers and cellular network providers, to create phones based on this new platform. This group is called the Open Handset Alliance. In addition, since Android will be so-called “open source” software, Google expects numerous developers around the world, large and small, to modify the operating system and create programs that will run on it.

If all goes according to plan, Google says it expects to see many different Android-based cellphones and other mobile devices, from a variety of manufacturers and carriers, in various designs and with differing functionality and capabilities. Some may be larger-screen “smart phones,” similar to an iPhone or BlackBerry. Others might be smaller, simpler phones. Still others might fall somewhere between an iPhone and a small laptop.

Google officials say they expect the first Android devices to be available later this year.

After reading your Jan. 3 column, I looked unsuccessfully for a Home and Student version of Office for Mac 2004. Does such a version exist?

In the 2004 release of Microsoft Office for the Mac, this low-priced version had a different name: the Student and Teacher edition. Microsoft presumably changed the name of this $150 product to the Home and Student edition in both Office 2007 for Windows and Office 2008 for the Mac, because, while it was technically limited for sale to families containing students or teachers, no proof was required and it was widely purchased by consumers in general.

However, there’s a big difference between the latest Windows and Mac versions of the Home and Student edition. In the Mac version, it includes Word, Excel, PowerPoint and Entourage, Microsoft’s equivalent of Outlook on the Mac, which, like Outlook, includes email, calendar and contact functions. But the new Windows version now omits Outlook, and instead substitutes OneNote, a note-taking and information organizing program that is far less commonly used. So, Windows users must spend much more money to get a version of Office that includes Word, Excel, PowerPoint and Outlook.

Is there a way to back up Microsoft Outlook Express emails, particularly Inbox items?

Outlook Express stores your emails in database files, with all the messages in each of your mail folders lumped into a single such file. These files can be backed up, or copied, onto other hard disks, or storage media.

The email data files are usually buried in obscure subfolders in Windows. But you can locate them by clicking on the Tools menu, then Options. This will open a tabbed window. In this window, click on the tab called Maintenance, then the button called Store Folder. This will generally give you a long, complicated path to the folder.

Next, copy this path by selecting it and pressing Control and C. Then, click on the Start menu, select “Run…”, and then press Control and V and then click OK. This should open the folder that contains your email. The inbox is contained in a file called Inbox.dbx. This is the file you will want to back up. If you want to back up other folders, such as the Sent mail folder, you will find them along with the inbox file, with the same “.dbx” suffix.

Some backup programs may automate this process by simply allowing you to designate that you want to back up your Outlook Express emails. There are even some programs specially designed to back up Outlook Express messages. You can find some of these by simply performing a Web search on “backup Outlook Express.”

• 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.