How can I undo initialize HDD to avoid file system errors?

Hi there,
I connected my Hard Disk Drive to a computer and went to the disk management and initialized the disk. After the initialization process, I realized that everything was in a disarray, I have not idea what might have happened, but the entire file system seems to be corrupted. Is there a way I can undo initialize HDD so that I can have everything back and working normally?
Thanks.
