The HP 100LX comes with a warranty that includes Express Exchange Service for the first year.
If you have a defective unit, call HP technical support at 503757-2004. They will determine if your unit is defective and arrange to ship a replacement unit to you via Overnight Express.
When you receive the replacement, take it out of the box, put your defective unit in the box, seal it and label it (tape and label provided), and then drop it off at the post office.
You can also purchase a Support Pack, which extends the warrantee and Express Exchange for two additional years for $85. Contact your HP Dealer within 30 days of purchasing your HP 100LX. After that, but before the end of the first year, contact HP Corvallis Service Center at 800-757-2004 or 503-757-2002.
This program is for the HP 100LX only. The above procedure is for U.S. customers; there are similar programs in place for other countries. Contact your local dealers.