Windows 7 - problem with bitLocker

Hi.

I have encrypted my external HDD with bitLocker.
It's 500GB and works perfectly fine with the computer encrypted it, but whenever I try to access it with other computers, it says the drive has to be formatted before use.

Can anyone help me with this please?
Thank you in advance.

Did you use Bitlocker To Go? or the normal Bitlocker?

Are your other computers also running windows seven ultimate? If not then you will not be able to unlock the drives on the other computers. I don't know if third party software on a non windows seven computer could either.

That's the whole (or almost the whole) point of bitlocker, i.e., to prevent someone on another machine from accessing your bitlocker encrypted drive. If you used "bitlocker to go" on the drive, you would get a prompt for a password when accessing the drive from other machines that, when entered, would give you read only access to the drive from other machines (not sure which OS's would allow access like this but I know XP is one).

I'm still thinking about whether and how I may want to deploy Bitlocker. I'm a little concerned about being locked out of my cloned system back up drive if my machine is stolen and I don't have the recovery info or flash drive available. And also whether having the drive so encrypted would interfere with effectively backing up the entire system so it could be recovered to a bootable state using Acronis for both cloning and image backups.

The drive, on autorun, should be prompting you to install bitlockertogo.exe whcih will allow XP/Vista to read Bitlocker To Go drives.

Well, assuming you used bitlocker to go and not standard bitlocker.