Why does my external drive disappear from my desktop?

Question

I am switching from PC to Mac. I have 2 externaldrives. Both have been formatted in FAT 32 by the MAC. When I plug them in the desktop and finder see them, then with both of them they have disappeared from the desktop and from finder. Still can be seen in disk utility and system profiler. How can I find them and why does this happen?

Answer 1

If you daisy chained then try without. May not be enough power to handle both at sme time. Other than that read some info:
1. Shut-down your Mac, and unplug the power cord
2. Turn the power off on your external FireWire devices
3. Unplug the FireWire devices from the Mac
4. Wait for 5 min.
5. Plug the power cord to your Mac only
6. For PPC Macs: Restart the Mac while holding the Option-Apple-O-F, and keep holding until you get the ">" prompt, then release the keys
7. At the ">" prompt type:
      reset-nvram and hit the Return key
      set-defaults and hit the Return key
      reset-all and hit the Return key
the last command will restart your mac
8. Shut down your Mac
9. Connect all your FireWire devices to the Mac and turn them on
10. Restart your Mac.
All your FireWire devices should reapear, if not repeat the procedure
How to avoid the issue :
The only really proven way to avoid burning up a FireWire port is to connect all devices and to turn them on PRIOR turning on the Mac. Likely, one must unplug them and turn them off AFTER the Mac has been turned off. If you need to connect another device, then you're on for a shutdown of your machine... 
It's a tad annoying but it guarantees that the FW ports won't be damaged. 
Be careful when using self powered devices such as webcams, iPods, hard drives or hubs, as they can destroy the port pretty easily. Another thing is to avoid daisy-chaining hard drives.
When the FW port doesn't respond anymore :
In this case, peripherals won't be mounted upon plugging, and won't be displayed in Apple's System Profiler. The self powered devices will still be fed by the port, but won't respond either. 
It happens that the PHY just hangs after a surge or a random problem. Once hung, the port will not respond any longer, it is possible to reset the component by going through the following steps :
1° boot the PPC mac in Open Firmware by holding [ Apple key - Option - O - F ] after the startup chime. 
2° you'll get to a command prompt. the keyboard mapping will be QWERTY, so pay attention when you type the following : 
RESET-NVRAM (enter) 
RESET-ALL (enter) 
3° Now the mac should restart itself and the port should function properly again. 
If it still doesn't work, then it means that the PHY is damaged.
http://www.hardmac.com/articles/16/
From Kappy post:
922 is only used in dual drive cases to provide a "build-in firmware RAID support"
912 or 912+ is FW800, the "+" means USB2
911 is FW400
924 adds eSATA support along with FW400/800
MacSales, OWC Tech Support library is where I would go first, as they do tend to have or links to, firmware updates for Oxford.
From Wiebetech:
I just upgraded my Mac OS, and now I'm having trouble with my FireWire device. What can I do?
A: With nearly every OS update Apple releases, some external drives are not recognized after the update. The typical symptom is that the device will not mount but the volume is visible and grayed out in Disk Utility. This means that the device is working properly, but the OS does not recognize the volume as mountable. Sometimes the drive does not show up at all.
The first thing to do is to see if repairing Permissions with Apple's Disk Utility First Aid feature solves the problem. If not, try repairing the disk with First Aid. Another possible solution is to zap the PRAM. This is done with a keyboard command while rebooting. Restart your computer and hold down the Command, Option, P and R keys. Consult the Apple web site for details.
If this does not work, then try pushing the PMMU reset button on the logic board. Consult the Apple web site for locations of the button for your Mac. If the drive still does not show up, shut down, disconnect all peripheral devices, and boot from the Mac OS Installation CD. The later the OS version, the better. Do not reinstall the OS, but when the Installer is loaded up and ready to begin, go to the File menu and use the Disk Utility program. Connect the drive that is having problems, then start the Disk Utility application. If you see the external drive and it is not grayed out, you know the drive is okay. Run Disk First Aid on it anyway. Then run it on your internal boot drive while you are at it. When done, unmount the external drive and UNPLUG it! Then restart the Mac.
When the Mac has restarted and is running on the internal boot drive, reconnect the external drive.