no os

heyy my blackberry curve 8520 has no os on it and when i plug it into the computer ther computer beeps because its plugged in but all software i try says its not there, blackberry desktop manager, bbsak crackutil ive searched the internet for days and i now dont know what to do am i wasting my time or is there a way to solve this please help. oh and ive also tried reebooting everything reinstallin everythin with the battery without the battery unpluggin and replugging the usb with internet without internet im stuck pleeeaaassssee help anybody :(