"The HP 200LX is an IBM PC/XT with 80186 at 8/16MHz, 640x200 CGA LCD screen, qwerty keyboard, numeric keypad, RS-232 port, PCMCIA Type II v2.0 slot. It has MS-DOS 5.0 in ROM. All this is in tiny form factor: 16x9x2,5 cm and 18oz. Runs off 2xAA batteries. It was in production between 1994-1999."
These pages by Mike Kopplin(http://www.technoir.nu/hplx/) offer a lot of information and programms for the HP200LX. I have got a report that the below mentioned MiniX issue isn't quite stable. At this page there is a version of MiniX , which will run stable on the LX which uses the dosminix file system. The kernel was modified by Mack Baggette so that it would work with the LX's eccentricities. Different sized versions are available for download(http://www.technoir.nu/hplx/minix.html) .
A description of "the PCMCIA and BIOS INT13 services necessary to boot MiniX on the HP200LX Palmtop from a PCMCIA ATA Flash Disk. These services should be equally useful for booting LINUX-86 (ELKS) on the HP200LX."
This HP LX 200 FAQ(http://www.hplx.net/faq.html) page contains the full "DOS-based LX series FAQ", the "200LX Power System FAQ" - Ian Butler's comprehensive FAQ about batteries, adapters, the "200LX Networking FAQ" - covers ethernet networking issues with the 200LX and the "Humorous HPLX-L Mailing List FAQ".
A mailing list about general topics with the HP 200 LX can be found at the HPLX-L Control Center(http://www.sp.uconn.edu/~mchem1/HPLX.shtml) . The archive of the list is available at HP 200LX page(http://www.technoir.nu/hplx/hplx-l/) by Mike Kopplin.
The Sharp PC-3000 and PC-3100 (PC-3k) are small 8086-class palmtop computers running DOS 3.3 in ROM, with 1 or 2 MB RAM, CGA LCD screen, 2 PCMCIA type 1 slots, serial and parallel ports, with optional external printer. They are supposed to ran MiniX with the 2MB image available for download(http://www.technoir.nu/hplx/minix.html).
Times2Tech(http://www.times2tech.com/hp200lx.html) sells a memory upgrades, a double speed upgrade and DC adapters for the HP100/200LX. Their memory upgrades range from 4-64MBs with 96MBs in the works. The HP200LX is the only palmtop currently supported for memory upgrades. They also supply 1350mah rechargable Nimh batteries for the palmtop.