Parallels does not recognize vista disk bootable

Hello,

i got a new macbook pro and bought paralles transporter software. When I try to migrate my vista hard disk to the mac (encrypted with bitlocker) I get an error message on the PC:

"The operating system Vista cannot be made bootable. All selected drives will be migrated on virtual hard disks. Are you sure you want to continue?"

I have no clue what this is all about, can anyone help? Please!

regards

Werner

PS: Creating an image through VMware fusion works, though this cannot be imported into parallels, as it say, that the image is damaged