when i try to format with another software it says in an ERROR "write protect" after i try to format.
Sounds like that's the reason why you couldn't format it on your mac, either. Somehow the disk became write protected. You'll have to check out the hard drive's manufacturer's support site to find out how to fix that.
Or find a different hard drive.
You can also check the security permissions of the drive by right clicking on the drive and choosing the security tab at the top. You just need to make sure you , as the user, has read write access to the drive.
Give this a try and report back.