Hi,

I recently ordered a desktop. It has 1 internal hdd. I just finished putting a nice, clean linux install in it.

However, I wondered if it is possible to disconnect or otherwise neutralize that internal hdd and use an external usb hdd as my "main" hdd in its place. Is that possible?

I would actually have 2 external usb hdd: a) the "main" hdd with the OS for booting which would replace the current internal hdd and b) a "secondary" hdd just used for data storage.

Surely, I could not be the 1st person in the world to have thought of this set-up. Am I? Where would I go to learn more?

Is this possible and if yes, then how could I "transfer" the contents from my current internal hdd to one of these new external usb hdd?

Yes there are possibilities:
1.) BIOS
2.) Lolevel format it
3.) delete the partition table with fdisk

but it concerns electricity till you screw open your computer and pull down the 2 plugs of that HD.

To copy all to a new location:
- start a linux on DVD system (Knoppix-5.1 is just pretty for such a task)
- mount the two hds
- open a root terminal
- type in #cp -ar from/a to/b //should work, make a test with /dev
- wait some hours ...

And yes, there is really no need of that - HDs are most internal.
External drives are most used to store changeable data (backup).
But the drives are so cheep that everybody uses hard raids.