The extremely irritating condition when a motherboard's power supply is controlled almost entirely by software. When (not if, WHEN) Windoze crashes, the power button will not respond (Since Windoze hasn't TOLD it it can shut down), meaning you cannot turn off your computer without reaching for the power cord and the <insert alternative-OS-of-choice here> disks.

Most boxen like this usually have a kill switch (i.e. Hold down power button for five seconds) for just such occasions. However, they are usually not documented well.

Yes, I think this is noded elsewhere... but where?

This condition is a feature ATX Form factor. It's actually not so bad, providing you know how to work with it. It's there for such fun features as wake on lan and wake on modem. If the opperating system is frozen, it can be turned off most of the time, by holding the power button for 3-5 seconds.

Source:http://www.duxcw.com/faq/ps/ps1.htm