imac 21.5 inch mid 2010, always no bootable device

i have iMac 21.5 inch Mid 2010

imac 21.5 inch mid 2010, after create bootcamp partition restart to install windows 7 pro 64 bits but no bootable device

any one can help me? ASAP please.

thank you

i try many time but same problem 😟

( remove and create Bootcamp partition but same : no bootable device -- insert boot disk and press any key )