QEvery time we run the disk defragmentation utility on our machine, this program reports that the disk has deteriorated within a week. What keeps fragmenting the hard drive?

AIn a word, life. Every time you run a program, create a new file or edit an existing one, the software on your machine must write new data to the hard drive. In the process, many files will be split into smaller chunks that can fit into separate open spots on the drive. (Many reporters use a similar system to organize papers on their desks).

This ongoing fragmentation of data can slow a computer down when the drive spends extra time reassembling files from widely dispersed locations. Defragmentation utilities address that situation by reassembling and regrouping files for more efficient performance -- but this takes a lot of time, and fragmentation resumes almost immediately afterward.

Both Windows XP and Mac OS X include their own basic defragmenting tools, and for most users they should be enough. To defrag a drive in Windows, double-click the My Computer icon (or whatever you're renamed it), right-click your drive and select "Properties . . ."; then click the Tools tab and click the "Defragment Now . . ." button. Mac OS X defragments files automatically.

You can invest in more advanced commercial defrag utilities, but the time spent installing and configuring them will probably exceed any time gained back from whatever performance boost they provide.

Can I keep the same set of Web bookmarks in sync between my copies of Firefox and Internet Explorer?

We reviewed one program, FavoriteSync (www.favoritesync.com), that does exactly that; it can also synchronize bookmarks files among multiple computers. Since that review ran, a couple of readers have suggested a Web site that offers similar capabilities: www.sync2it.com.

-- Rob Pegoraro

Rob Pegoraro attempts to untangle computing conundrums and errant electronics each week. Send questions to The Washington Post, 1150 15th St. NW, Washington, D.C. 20071 or rob@twp.com.