Volumes problem

A problem has cropped up that I've had to deal with in the past (never successfully):

Whenever I get in to a lot of file-downloading or copying between external harddrives inevitably I get this problem where the system starts copying files that I mean to go to an external drive onto an internal representation of that drive (hence, to say... Justin's Computer -> Volumes -> External Drive -> files).

Then when I manage to realize it's on the wrong drive, another "External Drive 1" folder is created in the Volumes folder. How does this "Volumes" folder work, and is there anything I'm doing to create this problem? And how can I fix it? Because these files are essential invisible to me unless I specifically look for them.

Thanks!

-Justin

The problem is probably due to detritus left over in the /Volumes folder from some previous incident when that drive was not properly unmounted.

First unmount and physically disconnect all external drives.
Then use the menu item "Go to Folder..." from Finder's "Go" menu, and then type in "/Volumes" (without the quotes).

Look at the contents of the /Volumes folder.
If you see anything other than the one entry for your internal drive, that is likely the detritus I spoke of above.

Use Finder to trash the left over folders from /Volumes. (If you are sure that no external disks are connected then this can't affect what is on the external disks.) Finally, empty the Trash.