A. The most likely reason your computer stalls is that another program, running in the background, is interrupting the defrag process. Try deactivating your screen saver and your antivirus program. There’s a good chance that will do the trick.

If that doesn’t work, you’ll have to experiment by manually halting various startup programs to see which one is the culprit. To do that, click on Start, Run, and type msconfig in the box.

Then click on the Startup tab, and a System Configuration Utility box appears with a list of all the programs that launch when you fire up your computer.

Unchecking a startup item blocks it from being launched when you reboot. As you can see, you won’t know whether you’ve found the offender program until you run defrag after the reboot. Yes, it’s a slow and crude solution, but that’s the price you pay with Windows.

A. XP typically finds such errors and fixes them on startup. However, if you’re still getting them, enlist Windows’ built-in Check Disk feature. While it’s a primitive tool, it works and costs nothing. To access it, go to Windows Explorer or My Computer and right-click on the drive letter that is experiencing errors and then click on Tool, which will evoke this screen:

After you enter checks in both boxes on the screen and then click on Start, you will be instructed to restart the computer. As it reboots it will perform a check of your hard disk and repair any errors.

More effective, and faster, repair tools also are available with Norton Utilities (www.symantec.com) or OnTrack SystemSuite (www.ontrack.com).

A. You’re right on both counts. It can be a confusing tool, but once you learn how it works, you’re sure to find it very useful. It saves you from going into Format every time you want to set a margin or indents. With Ruler, you can perform many tasks with just a few mouse clicks. For an excellent tutorial on how to use Ruler, check out this Web site: www.mvps.org/word/FAQs/General/UsingRulers.htm.

A. Well, it may be a bug. But I’d guess your mouse needs some obedience training. First, try using the F8 key that many of us once used in WordPerfect to control the highlighting of text. Place your cursor where you want to start highlighting and press F8 once.

Notice that the EXT mode indicator, situated at the bottom of the screen, is activated. Then, using either your mouse or the keyboard, move to where you want the block to end, and do what you want to do: copy (Ctrl+C), cut (Ctrl+X) or paste (Ctrl+V). When finished, click on Esc to deactivate EXT. In Excel, EXT is canceled by pressing on F8 again.

If that doesn’t solve your problem, the next option is to train your runaway mouse. Click on the Start button, then Settings and Control Panel and then Mouse. Now click on the Wheel tab (see screenshot above). Notice you can control the number of text lines (or cells) that will scroll for each notch movement of the wheel. You also have the option of moving a full screen at a time.

While you’re in the Mouse Properties screen, check out all the other tabs and fine-tune the mouse controls to your liking. You may even want to change the cursor icon or, if you’re left-handed, switch the mouse buttons. You also can adjust the double-click speed and turn on a lock so you don’t have to hold down the mouse button when you click and drag (see screenshot at left).

A. You have at least two options. One is to comb out all those unnecessary files and applications that are probably crowding your hard disk. While cleaning is easy and costs you nothing, as a practical matter, it won’t gain you very much space.

Adding external storage is the best longer-term solution. In effect, what that does is add another drive to your computer. So, for example, if your main drive is C:\, adding external storage will give you a D:\ drive, which can be the location for both files and applications. You can then either download many of your less frequently used files and store them on the external drive or you can leave the external drive semipermanently attached to your desktop and actively work on files or even new applications stored there. Adding an external memory is very inexpensive, easy to do and will not even slow your computer.

Let’s talk about cleanup now. It’s something you should do under any circumstances because it’s just good housekeeping. All computers create temporary files as you work. In theory, Windows should get rid of them when they are no longer needed, but Microsoft, being what it is (slightly buggy), often leaves its detritus behind.

Many utilities, such as Norton, have functions that let you perform a cleanup with just a few mouse clicks. Windows also has a fairly automated method; to activate it, follow these steps.

Go into Explorer (or My Computer on the desktop), right-click on your main drive icon (it’s probably C:\) and choose Properties (see screenshot above).

Then click on Disk Cleanup, which produces the screen wizard at left.

Notice at the top of the screen that the wizard indicates a complete cleanup would free as many as 314,078 kilobytes of disk space. But it’s not prudent to remove all “unnecessary” files; some are still useful. Here are the ones I would remove (by placing a check in the adjacent box): Temporary Internet Files, Offline Web Pages, Debug Dump Files, Recycle Bin, Temporary Files, Temporary PC Health Files and WebClient Publisher Temporary Files. Leave the others alone; you may need them in the future.

If your version of Windows lacks this wizard, you still can do the same cleanup, but it’s going to require a few more steps. Go to Explorer and click on the Search icon, producing the screen below.

Under What do you want to search for? click on All files and folders. Under Look in:, use the down arrow to set the selection to C:\, or just type it in. And then, under All or part of the file name:, type in *.bak, *.tmp, ~*.* (see screenshot below). That tells Search to locate all backup (bak) and temporary (tmp) files and any copies of files Windows accidentally left behind (signified by the tilde (~)). The asterisks (*) are wild cards, telling Search to find any files with those attributes.

Then click on Search and wait for the files list to appear. Don’t remove any temporary files dated as recently as yesterday. To find the older ones, click on the Date column to sort the files in date order. Then select the first file you want to delete, hold down the Shift key while hitting End (which takes you to the end of the list) and press Delete. Don’t panic if you get a message that one of the files is in use. Just repeat the process as many times as necessary. When that’s finished, click on your Recycle Bin and empty all those just-deleted files.

Because of the volume of mail, we regret that we cannot individually answer submitted questions. However, if a reader’s question has broad interest, we will answer it in a forthcoming Technology Q&A column.

On occasion you may find that you cannot implement a function I describe in this column. More often than not it’s because not all functions work in every operating system or application. I try to test everything in the 2000 and XP editions of Windows and Office. It’s virtually impossible to test them in all editions and it’s equally difficult to find out which editions are incompatible with a function. I apologize for the inconvenience.