Problem in formatting my external harddisk

Hello, mam/sir, i really need your help, i have this external harddisk (250GB) i format it because some of my files are corrupt i don't know why, the last thing i have done is i'm just copying files on my computer then suddenly a pop out message appears that i can't copy the file from my computer to my external harddisk, i format it then its stops in 8%, i wait for 30 mins and still in 8% condition and again i wait for an hour but still in 8%, how can i fomat my external harddisk??? please... i need help.... =(