My Dell Dimension L800CXE shuts down unexpectedly. I
called Dell Technical support, and the support person had me reseat the
sound board, modem board, and NIC card. Then she had me reboot the computer
with the Dell diagnostic CD. The diagnostic program found no errors. The
computer worked fine for a day or so then it shut down unexpectedly.

The first time I noticed the monitor was blank and the power light on the
tower was flashing.
I tried to move the mouse. Nothing
I tried pressing a few keys on the keyboard. Nothing
I tried to hold the power button in for a restart. Nothing
Then I unplugged the computer and plug it back in.
I started up into Windows ME and worked fine for about 7 minutes
Then it shut down just like it did before.
I left it unplugged overnight.

The next day I plugged it back in and it started up into Windows ME.
Browsed on the internet for about an hour and a half then the same thing
happened,
The computer unexpectedly shut down. Power button light flashing, no
response from the keyboard, and no response from the mouse.
Again I had to unplug the computer and replug it in again.
It lasted for I guess about 10 minutes then it shut down again.

The next day I called Dell technical support. (See above)

After that, the computer was on for about 24 hours then it shut off
automatically.
After it set for a few hours I turned it back on and it been running for a
little over an hour. I had better send this message now before it
automatically shuts off and I lose everything.