Would you think choosing one OS over another could have an impact on the warranty of your computers hardware? Obviously it shouldn't, given that software is the superficial interface between the two and can't exactly control whether or not a monitor explodes or a CPU is defective. However, HP seems to disagree. By installing Linux on a Compaq Presario laptop, a lady voided the hardware warranty. Despite the laptop being listed as “Linux ready” (which usually means it met all the hardware compatibility requirements), a problem as mechanical as sticking keys will go unfixed unless you wipe Linux and restore the original OS:

When she called Compaq -- the unit comes with a one-year warranty on the hardware -- they asked what operating system she was running. When she told them Linux, they said, "Sorry, we do not honor our hardware warranty when you run Linux." In order to get warranty service, she was told, she would have to remove Linux and reinstall the original OS.
A PR rep stated that is pretty much par for the course, and that yes, hardware warranties can be invalidated by your choice of OS. What is scary, however, is the wording chosen – making it sound that the warranty terms are vague enough to make this apply to any piece of software they might not approve of:

The PR rep told me, after wading through all the terms and conditions attached to the notebook's warranty, that "it is impossible to anticipate every single issue that a customer can face, so the terms and conditions of warranties can't list every possible scenario. Usually if a customer installs a different OS, it has a big impact on the PC and will void the warranty.
Of course, it seems you always have the option of restoring from the restore discs provided with your laptop (or burned yourself with many of the newer ones), at the cost of wiping your old install. So what happens at the other end of the extreme – machines sold with no operating system?