Yesterday I was playing with my new system and decided to take a break. I logged out but did NOT shut down the system. I have heard many stories about Linux systems running for many months without issue so I thought it would be no problem. After an absence of ten to fifteen minutes I remembered that my monitor is an LCD and that their lifetimes are measured in how many hours they are on. The monitor cost me too much money to allow it to just sit, so I decided to turn it off. When I returned to my computer the LCD image looked like a TV with bad horizontal adjustment.
I thought the computer had simply gone to sleep and would awaken when I moved the mouse or hit a key. Nope, nothing happened. I could not get a response from the computer from any keys or key combinations including CTRL-ALT-Delete!
Well, I finally decided to just turn the power off despite knowing that this is BAD for Linux systems. ( Any ideas on how I could have recovered from this? I thought Linux systems could stay on indefinately. )
Now we get to the meat of this post. When I tried to power up my system after shutting it down it went through the normal POST and then started writing an L 99 99 99... for nine and a half lines after which it would pause a moment and then repeat the sequence.
This was not a big problem for me, I simply re-installed. But, what happens if several months down the road, after I've built up a large collection of files and data and I suffer through a power outage? Do Linux users have to invest in a UPS?

L99 ... is a lilo bootloader problem. It could of been fixed by booting the 1st CD to rescue mode and reinstalling lilo to the MBR.

Journaling filesystems recover better and faster then just a plain ext2 but besides some apps having to be reinstalled my systems have never crashed due to a power failure. But not that it can't happen.

If you intend to keep your system on 24/7 I would invest in a UPS. Brownouts and power surges can damage hardware too.

Sounds like you have a apm,acpi problem.

If you choose a journaling file system such as reiser or ext3, such problems shouldn't really happen. My kids have powered one of my PCs off because they thought it wasn't on - no problem, it's happened several times.

If you find yourself in that identical situation, Ctrl-Alt-Backspace should kill the x-server, so you can startx again, or reboot or shutdown cleanly.

Well diagnosed Michael!

To further add, I've had my system get unceremoniously "powered down" on two occasions now (the black out once, and my wife once not realizing the system was just asleep). Both times it recovered flawlessly, and I've watched it happen in other (non-Mandrake) systems as well, so I think that although it isn't something you want to make a habit of, it's not the end of the world.

Thanks to all for the comments. I'm a complete newbie, so the information about apm, acpi, and Ctrl-Alt-Backspace was good.
I was given the option of checking a box labeled ACPI during installation. I chose not to check it. Was that good or bad?

before i installed madrake (i'm still on dual boot..), i experienced a similar problem using win98se. there's a power switch in my room looking just like a light a light switch, so whoever wanted to turn off the lights (when i wasn't there...) turned of my computer!!!! after it happened couple of dozen times, my power supply unit started roaring and making other strange noises. every time i used more than 1 app it shut down all by itself. finally, it started smelling, like burning plastic - and there went my power supply unit...
i had to take it of and buy a new one....