I have a 3-year-old PC, which has a single physical hard disk divided into a small C drive that is almost full and a larger D drive that has lots of empty space. I know I can move stuff from C to D, but how can I either merge these hard drives or somehow make D the automatic destination for files I download?

You can merge the drives into one larger C drive, or redistribute space between them, by using what’s called a disk-partitioning utility — a program that rearranges the space on the hard disk without erasing your files. One I have tested and found that works well is called Partition Magic and is sold by Symantec.

Short of doing that, you can change the settings in programs you use to download or save files so that they store the files on your roomier D drive. Not every program has such a setting, but many do. These settings are usually found in the options or preferences sections of the software. For instance, in the latest version of the Firefox Web browser, go to the Tools menu, select “Options,” and, under “Main,” in the Downloads section, you can specify a folder on your D drive where it says “Save files to.”

In your review of the Amazon Kindle e-book reader, you praised its ease of downloading books, but criticized the hardware design. You seemed to prefer the design of the Sony Reader, which costs $100 less, but said it offers fewer books. If you had to choose between them, which would you pick?

Neither is a compelling product. However, putting aside price as an issue, I would choose the Kindle, despite its design problems. The Sony is slimmer, sturdier and, unlike the Kindle, it isn’t prone to accidental button-pushing. But Amazon’s device can download books directly, without the need for a PC. Sony’s can’t. And Kindle’s online catalog of compatible titles is 90,000 books, more than triple the number Sony offers.

Unless you absolutely crave an e-book reader now, I’d suggest waiting for a system that’s better than either. However, if you’re going to invest $300 or $400 now in a device to read electronic books, you would likely want the one with the widest selection of titles and the quickest, easiest downloading process. And that’s the Kindle.

I use Outlook Express for my email. I have been getting a lot of offensive junk mail I’d rather not even view for a moment. Is there a way to delete incoming mail in Outlook Express without having to first view the contents?

You can avoid automatically viewing the contents of your email in Outlook Express, and many other email programs, by turning off the preview feature. In Outlook Express, click on the View menu, then select “Layout…”, and uncheck “Show Preview Pane.” Then, click OK. After that, you will have to manually open each message to view its contents.

However, you may have to open some emails anyway in order to decide whether to delete them, since spammers often use deceptive sender names and subject lines that make it hard to decide if they are worthy of deletion. So, you might consider installing an antispam program.

You can find Mossberg’s Mailbox, and my other columns, online free at the new All Things Digital Web site, http://walt.allthingsd.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 antispam systems, programs to transfer files from PC to iPod and the VoiceOver system on Macs.

What is the best antispam system out there today? Spam filters don’t seem to work well for me.

Spammers change tactics so frequently that even the best, most adaptive filtering systems have a tough time coping. In my view, the strongest antispam approach isn’t filtering at all, but is called a challenge-response system.

With this approach, you set up a “white list” of approved senders — it could be your address book or some other list — and every email you get from anyone who isn’t on the list gets challenged. What this means is that the incoming email is intercepted and that the sender receives a message asking him or her to enter a constantly changing code number to prove that the message originated with a human.

The computer programs that blast out millions of spam messages usually can’t type in such a number, because it is presented as a graphic and in a wavy or faint typeface, and computers typically can’t copy and paste such graphical numerals automatically.

Messages that pass the challenge are delivered to you. Those that don’t, including nearly all spam, aren’t. Examples of such services are ChoiceMail, at digiportal.com; and EarthLink antispam, at earthlink.net.

The downside of this approach is that legitimate senders not on your list may find it a hassle to fill out the challenge and give up on emailing you. This is a problem mainly for business users who get desired emails from people they don’t know, such as prospective customers.

I would like to transfer files onto a new PC from my iPod. Are there any programs that do this?

There are multiple inexpensive programs designed to do exactly that. Some work with Windows computers, some with Apple Macintosh computers, and some have versions for both. One that I have found reliable is a British-made program called Music Rescue (formerly known as PodUtil) and can be found at www.kennettnet.co.uk/musicrescue/. It comes in both Windows and Mac versions and costs £10, or about $19.40.

Ever since I changed batteries 10 days ago in the wireless keyboard for my Apple iBook G4, there has been a voice that seems to be issuing commands to the computer, or at least is speaking what is happening when I do things. I must have done something wrong. How can I stop it?

I assume that, while fumbling with the keyboard to change the batteries, you accidentally turned on a feature called VoiceOver in Apple’s Mac OS X operating system that speaks aloud various alerts and actions. This feature is intended for certain disabled users who have difficulty seeing the screen or otherwise could benefit from spoken feedback when navigating their computer’s interface.

To turn VoiceOver off, you can just press the command (Apple) key and the F5 key simultaneously, though on a laptop such as yours you may have to also hold down the Function (fn) key at the same time. Or, you can launch System Preferences, select Universal Access, and then select the tab labeled “Seeing” and click the Off button under VoiceOver.

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Because of the volume of e-mail I receive, I can’t routinely answer individual questions by e-mail, 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