I have a Dell Dimension that is six or seven years old. Recently, the following message appears every time we start the computer: “WARNING: Dell’s monitoring system has detected that Drive 0 on the primary EIDE controller is operating outside of normal specifications. It is advisable to immediately back-up your data and replace your hard disk drive.” When we hit F1, the computer boots normally and functions fine. All our data is backed up on an external drive. What is going on? Is it time to bite the bullet and get a new computer?

I don’t know exactly what’s going on, but you should take the warning very seriously. It’s good that your data is backed up, but if your hard disk fails, you won’t be able to use the computer. Six or seven years is a long time to keep a computer, and hard disks do go bad. Just because it continues to work doesn’t mean it isn’t on the verge of sudden failure. At the very least, have Dell or a local technician diagnose the hard disk to see if it is a serious problem or one that can be easily fixed. If the disk is failing and you are otherwise perfectly satisfied with the computer, you can get a new drive that is much larger for a reasonable sum. You should also seriously consider buying a new computer, simply because everything else on your machine is also out of date and, as time goes on, you may find that more and more software and Web sites won’t work well with it.

Does either Parallels Desktop or VMWare Fusion support multiple virtual machines installed on a Macintosh — for instance, one running Windows XP and one running Windows Vista?

Yes. Both of them allow you to create multiple virtual computers, running Windows XP or Vista, older versions of Windows, or Linux, as long as your Mac has sufficient hard-disk space.

My Toshiba Satellite runs Windows XP Home, and it takes more than four minutes when starting up before I can open any programs. Is my computer running too many programs at start-up? If so, how can I view them and shut down the unnecessary ones?

That certainly could be one cause of the problem. It’s a common situation. To see what programs are set to run when you start up your computer and to turn off unwanted ones, you can use a somewhat geeky built-in program from Microsoft or simpler ones available from outside software vendors. To run the built-in program, go to the Start Menu, click “Run,” and in the blank box that appears, type in “msconfig.” This utility will let you turn on and off invisible start-up programs. Go to the tab marked “Startup” and check off any you don’t want. But be conservative — don’t turn off anything you don’t recognize and know is unneeded. A better solution, easier to use and with more information, is an $8 utility from PC Magazine called Startup Cop Pro. You can get it at: www.pcmag.com/article2/0,1759,2177188,00.asp. There are a number of similar programs that may work just as well, but unlike Startup Cop, I haven’t tested them and so can’t recommend them.

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

If you have a question, send it to me at mossberg@wsj.com, and I may select it to be answered here in Mossberg’s Mailbox.

Recently, my laptop is taking an inordinate time to boot up. I have tried disk cleanup, defragmentation, and multiple scans by antivirus programs but nothing seems to speed up the full bootup process. Do you have any suggestions?

This probably indicates that you have a large number of programs, many of them invisible to you, that are configured to launch at startup. Some may even be spyware and adware programs. I suggest two steps. First, get a good antispyware program, like Webroot’s Spy Sweeper, and do a thorough scan of your system, deleting all the spyware and adware you can find. Spy Sweeper, which costs $30, is available at www.webroot.com. (A free trial is available.) Then, reboot.

If the system continues to reboot slowly, you should run a program that tells you which programs are trying to launch at startup. Get rid of those you don’t need. A built-in Microsoft utility, msconfig, can do this for you. Just select Run from the start menu and type “msconfig.” Look over the programs listed in the “Startup” tab of the program, and uncheck all that you’re sure you don’t need. This may be tough, because msconfig doesn’t give the English names of the programs or explain what they do.

Even better, download and run a startup utility like Startup Cop, which explains things better. It costs $5.97 and is available at www.pcmag.com/article2/0,4149,2173,00.asp.

We would like to use the Internet wirelessly in our home, but we have a dial-up service. We were told by others that one has to have a cable or DSL modem to go wireless. Is that true?

No, you can do it with dial-up, though the speed is so slow that the experience over wireless may be disappointing. A company called Always On Wireless makes a wireless base station called the WiFlyer that is specifically designed for sharing dial-up connections wirelessly. It costs $150 and is available at www.wiflyer.com. I have seen it demonstrated, and it worked, but I haven’t tested it.

I run Windows XP home edition and also Word. After installing a newer edition of Word, I began to have a problem when I went to look for my newly prepared files. They don’t show up in the folder that I thought I put them in. How can I resolve this aggravating problem?

In Word, go to the Tools menu, and select Options. Go to the File Locations tab, and click on Documents. Set the location for saving documents to whatever folder you prefer, and click OK or Close until you are out of the Options window. That should take care of it.

* * *

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