External hard disc unseen

Hello, i have aspire v3-571G i-5-3210M 2.5 Gh and i have windows 7 ulti 64 bit
i have an external sata 250 mb
I have done the driver search and i have reinstalled the drivers from control panel and still i can not see my external drive in bios.. i haven't seen my external drive into another pc yet but i ve never used my hard disc since september . back then it was recognized.. i think it is something with the drives what else i can do.... Also i had gone into the acer site to checked the usb drives installed them but still nothing happened ( i do have driver genius driver max and driver cure to find any drives) so i dont know what else to do. please help me. Every time i cable my external hard disc i see the blue light but dont hear the noise from my pc.

thank you