You are, of course, absolutely right.

The alternative would be to quote the volume's path, like so:

sudo mdutil -i off "/Volumes/My Passport 4"

(My mistake was to have experimented on a volume whose name contains nothing requiring escaping; all my volume names are space-free.)

Thanks for adding the alternative syntax, using the " characters to enclose the complete volume pathname.

For the record, another way to deal with the escapement is to type this much of the command:

sudo mdutil -i off

Leave a space after the second f, then drag the icon of the volume to the Terminal window. The entire pathname, with escapement, is pasted for you.

Ok when i try that in terminal, i get this

Error: unable to perform operation. (-107)
No index.

also when i try disk warrior i get the following message:

The directory of the disk "my passport" cannot be rebuilt. The disk is still in use. Quit all other applications, or restart from the DiskWarrior disc, and then try rebuilding again. If you report this year, please mention the error code (2153, 4903).

I also tried calling western digital but their reps aren't knowledgeable at all

If you are using Leopard, see if these Terminal commands work:

How to turn Spotlight OFF (and ON Again)....Leopard Solution

The advantage of this approach is that it is global, requiring no interaction with a particular volume. A log out and log in, or a restart, may be required for the change to take effect.

Ok I turned of spotlight and tried to eject. My passport folder is still empty and it would not eject and said it's still in use

I ran a sudo lsof | grep on the passport to see what's using it and nothing shows up which I guess is what we wanted. But it still says it's in use.

Might I add that when plugging the external drive to other macs, I get the same problem.

Did you try the Safe Boot?

Is there some software that Western Digital installs either on the boot volume or on a volume on the drive itself?

yea safe boot didn't work. About the software, it's called WD manager and all it really does is show how much space you have left on the drive. I don't think it's a problem.

If WD manager cannot be stopped, the volume is always in use. Try finding it and forcing it to quit in Activity Monitor, located in /Applications/Utilities.

Do you have the latest firmware for the drive? See:

http://forums.macworld.com/message/653126

I tried to find the latest firmware update but couldn't. If the latest firmware is the WD Drive Manager, I tried that but didn't work..

My icons in My Passport folder are showing up once again. However those folders are all empty.