My Mac HD not working

suddenly my Lion OX system do not upload and only white screen coming , the system not loading .

i try to recover the disc through test utilities and show there are several disc permissions problems .

the disc repair button was not activated to fix this problem , so i put a new HD and instal lion mountain OX 8 , and i connect the old Mac HD as external HD so i can get my old files and copy them to the new disc.

problem : the mac do not i recognise the old HD , and i could not find it .

kindly help me to restore my old files

using :

Mac book pro OX 8

8 GB RAM

2.4 GHz i5

thanks in advance