Storage Solutions HELP!!! Need To Recover Files From My Failed HDD


Hello guys,
Recently my hdd crashed. it's about 500GB ( seagate ST3500418AS, PCB No: 100361017) . It's still in warranty period so i can replace it . But the real problem is that i lost all my files, my personal, professional all kinds of files . It shows up in the bios when it's the only hard disk connected to the computer. when i try to boot using another hard disk . the failed hdd is not even showing up on my bios . So i only connected my failed hdd and tried to boot using hiren's CD Mini XP . it took almost 1 hour !! to finish loading the mini XP . but after loading i can see all the partitions and files of my crashed hdd . Then i connected a USB external hdd and try to copy files . but it takes almost eternity to copy even a 10 mb file. it's too slow and i have atleast 300GB data to copy . I know there are DOS programs in Hiren's CD . but DOS programs always confuses me . I have no idea how to use them

I really need to recover those files then only i can try to replace the hdd. the warranty ends in feb 2013. I still don't have the slightest clue about how to recover those files . So i need your help guys.

1: why is it not showing up in bios when i'm trying to boot using another hdd? . bios only recognize it when it's the only hdd connected to the computer
2: Which is the most efficient software to recover those files. I'm really a noob in these matter so please explain the procedure

Please help in whatever way you can....... i really need it