One of the smallest small-form-factor PCs you'll find is the aptly named Little PC from Stealth Computer. Measuring as tiny as 1.6 by 5.7 by 10 inches and weighing between three and five pounds depending on the configuration, the Little PC is primarily intended for use in kiosks, marine craft, aircraft, and embedded-control applications. Nevertheless, it could just as easily be the ideal solution for space-challenged home or small-office users.
Upside: Stealth offers a variety of configurations to meet your computing needs. Prices range from $895 for the LPC-301 base unit (which employs a 1.2GHz Pentium III processor and the Intel 815EG chipset with integrated graphics, 256MB of PC133 SDRAM, a 20GB hard drive, a 24X CD-ROM, and no operating system) to $2,060 for the LPC-401 pictured here (with a 2.8GHz Pentium 4 CPU and the SIS 651chipset, 1GB of PC266 DDR memory, a 60GB hard drive, a DVD/CD-RW combo drive, and Windows XP Professional). All units come equipped with a useful complement of ports, including three USB 2.0, FireWire, Ethernet, parallel, serial, and two PS/2.
Downside: You can pretty much write off any notion of future expansion: even if you could open the case--a feat in itself--you're not likely to find any room for growth inside, although the Pentium III-based LPC-201 unit does come standard with two half-size PCI slots. Also, be prepared to pay a premium for the system's minuscule mass.
Outlook: If you need a PC that can sit inside a shoe box--or be transported in one--a Little PC could go a long way.