Compared with the tower-case computers that squat under desks in millions of homes and offices, the tidy black box I have set up at home is a midget of a machine. Not only does this desktop actually fit on top of a desk, at roughly 71/4 inches tall by 77/8 inches wide by 12 inches long, it takes up no more room than many shoeboxes.

And at roughly 11 pounds, it weighs less than some laptops; its manufacturer even sells bags and backpacks to carry it around.

This computer didn't come from Apple or Sony, the two most prominent dissidents from the PC industry's beige-box orthodoxy -- although it's unmistakably reminiscent of the Power Mac Cube, Apple's brief experiment at building an ultra-compact desktop.

But where Apple's jewel-like machine debuted at $1,799 and never got cheaper than $1,499, Shuttle Computer's XPC line of desktops starts at $699.

This Taiwan-based manufacturer has sold these models to other manufacturers and in unassembled versions to hobbyists for the past several years, but recently began offering complete systems in some stores and on its Web site (www.us.shuttle.com).

To judge from the computer the company loaned, a $1,100 G4 6100M running Microsoft's Media Center edition of Windows XP, Shuttle's designs are every bit as usable as traditional configurations. This machine includes a powerful processor, a capable graphics card, copious amounts of storage -- just under 150 gigabytes of room on the tested PC -- and numerous connections for peripheral gadgets.

But for all its clever engineering, the XPC also seems a few ingredients shy of being ready for the mass market. It's a machine better suited for enthusiasts and tinkerers (such as the reader who e-mailed me to explain how he'd added a Shuttle computer to his home theater to manage his digital-music library).

Shuttle fits the essentials of a desktop in the XPC's cramped quarters with some crafty engineering. For example, the processor is kept cool -- not an easy feat with the tested XPC's 3 GHz Pentium 4 -- using a system of tiny metal pipes that conduct heat away from the chip and toward one moderately hushed fan, instead of the usual, raucous array of fans.

(This machine's overall quiet is undercut slightly by the way the power supply's own small cooling fan continues to whir quietly even when the computer is in sleep mode.)

Where compromises were necessary, Shuttle opted to include only items that most customers actually need. There's only one CD or DVD drive (a DVD+RW unit in the model I tried), but that's enough unless you routinely duplicate discs. Instead of a floppy drive that will collect dust in most homes, the XPC includes a memory-card reader that accepts most cards used in digital cameras, MP3 players and handheld organizers.

A single PCI expansion slot is left empty on the inside -- one more than most home users will ever use -- while an AGP slot accommodates a video card. Two memory slots are included; they're much easier to reach if you move the stack of CD/DVD burner, card-reader module and hard drive out of the way (a task that requires undoing two screws and sliding that assembly up and out of the case).

Most of the expansion potential here comes on the outside: four USB 2.0 and two FireWire ports (one of which is a full-size, six-pin model that can provide power to peripherals like iPods or external hard drives), plus two PS/2 connections and a serial port for any older peripherals. Best of all, two of the USB ports, one of the FireWire connectors and all of the standard audio jacks are parked right on the front.

But if you don't have a broadband Internet connection, the XPC is not for you -- it doesn't include a modem. If you need to dial up for your Web access, you'll need to put a modem into that PCI slot or plug an external model into one of the USB ports.

Shuttle says it can't include a modem in its motherboards, as almost all manufacturers do, because that would stop it from being able to use the same basic component in all its models worldwide. It also argues that its tech-savvy users ditched dial-up years ago.

That's most likely true (Dell's Dimension XPS, a powerful desktop marketed to hard-core gamers, also omits a modem in its default configuration). But for the rest of the market, giving up a modem entirely requires a big leap of faith.

The packaging of the tested machine is another potential obstacle. Its relatively thin load of bundled software didn't include any antivirus software.

This computer also exhibited serious quality problems. The card-reader slots didn't work until I opened up the case and noticed that one data cable had detached from its socket. The bundled wireless mouse and keyboard kept losing contact with the machine for the first few days until, for whatever reason, they began acting normally. When I plugged in a set of headphones, I heard an annoying background buzz and static even when nothing was playing on the computer.

Even the toll-free tech-support phone number listed in the System control panel was incorrect (the right one is listed online, and the folks there picked up in seconds both times I called).

And as I was wrapping up this review, I found that inserting a CD began to freeze up the entire machine -- the kind of random hardware glitch that should have gone out of style years ago. Shuttle says it has just switched to a different model of DVD+RW drive to fix this problem.

Defects like those, if at all common, can frighten away customers. But they don't impeach Shuttle's basic design, which other manufacturers could learn a few things from.

Living with technology, or trying to? E-mail Rob Pegoraro at rob@twp.com.