Unable to access Hard disk. I have this problem with my hard disk. The computer is able to detect

Question

I have this problem with my hard disk. The computer is able to detect the hard disk but I can access it as it says a corrupted or unreadable volume. I do not wish to format my hard disk as valuable data are in it. Do I have to send for a data recovery (which will cost a bomb as it is 250Gb) or are there a software with I could use to repair and recover my files? Thanks so much.