OK, here is how it all went down, but before I begin, I urgently need help to make sure something like this does NOT happen again. OK, so I run Fedora 11 on this desktop, with the following specs... 512MB of RAM 1.5 Ghz, Pentium 4 CPU, Can't find brand of PSU, three hard disks, one 80GB ATA Maxtor, and two old 4.8 GB SCSI IBM drives. I left my system running for about 10 hours, note that I have left it running for weeks at a time, and when I got back, I wiggled the mouse, changed my wallpaper (I do this often) and opened firefox. I then went to re-connect our router (I was offline) and when I came back, firefox had hung. I clicked my force quit applet, and it stayed pressed. I then hit CTRL-ALT-BACKSPACE, to see nothing happen. I then hit CTRL-ALT-F2, which got me to a text mode login. I tried to login as root, but after typing root and hitting enter, I was given no password prompt. I then hit the reset button on my PC, and it loaded the kernel and tried to start udev. This is where it got horiffic. I then heard all three of my hard disks seek at once, and udev did not start. I held down the power button until it powered off, and shut down the socket bar until I saw the green light on the motherboard go out. I hit it back on and powered up. It booted OK, until I chose my username at the login. Then again was the horiffic seek sounds, and it hung once again. The last boot was the scariest. I was given the hair-brained idea to stop the bootloader at the menu and wait. Here is what made me literally scream. After less than TEN SECONDS, the evil sounds occured, without the kernel even loaded! I hit enter to see what would happen, nothing. I pulled the plug, ripped off the faceplate and disconnected all drives, including the CD-ROM drive. I then called my old friend Mike (removed by request) to see what his take was, he was blank, and spent about 45 Mins going "umm... well, huh." until we ended up talking about my brita pitcher. After I got off, I re-connected my drives, booted, all was fine, started firefox and decided to post this on LQ. Anyone?

Last thoughts: All the things that happened remind me of the results of yanking a USB drive out when linux is booted from it. It seems to have lost it's root FS connection, but on all three drives? This is NOT a RAID array.

Since all three disks are resetting, then one would be looking at the motherboard or the power supply. Given that it happened several times in a row only a few seconds after restart, and is intermittent, one would suspect an overheating component.

My money would be on an overloaded power supply, given that there are so many drives plugged in. Most of the capacity is in the Maxtor drive - I take it there is a reason for keeping the two old SCSI drives going as well?

What is the power supply wattage? Did it happen on a hot day? Are the power supply and CPU fans working?

There is a reason to keep the SCSIs in. I use them to store stuff like ISOs, because I do need the space. My PSU is 300 watts. I have had those SCSIs running for quite a long time, so this was horrifying.

FORGOT: No, it was indoors with great air conditioning, and the drives were barely warm. I have arguably too many fans in there, but they have been there for a while as well.

I had a similar problem some time back and I learned that I would forever only buy a power supply that had a 5 year warranty....I learned that cheap power supplies generally have cheaper components and this means the output capacitors degrade over time. This then allows more ripple to occur and I found out the big capacitors on my motherboard were being "cooked".Excess ripple overheats the caps and they die sooner. I had funny booting problems where the hard drive would seem like it was throwing its search head all over the disk. I opened up my box and put my ear down near the hard drive and then could smell something cooking. I touched the caps on the motherboard and one of them burnt my fingers. Anyway, I thought I could get the capacitor replaced but it was more expensive to repair than to buy a new motherboard. When I got the new motherboard I also bought the much better (more expensive) supply with the 5 year warranty. It will have better capacitors and keep the ripple lower for a longer time. Anyway, I replaced the motherboard and PSU and everything booted without any noise in the hard drive. The hard drive booted without a reinstall of the OS. Anyway, I cannot conclusively say your power supply or motherboard are bad; just relaying my experience a few years back.

Do you have a live CD version of your OS handy? Try booting from that and see if everything behaves. I also had a problem just months ago when I would plug in a USB hard drive and the drive would sound like the head was clunking. But with the live CD it went away. I talked with a friend who was more savvy than me and he told me to run fsck on the boot drive.
You do this from the live CD but must unmount the drive first. fsck found a number of corrupted files and repaired them. When done I then rebooted from the hard drive and the problem with USB drive clunking was gone.