I have i problem in my computers in drive 'D'

Hello,

I am majid from kashmir,i am suffering from a big problem in computer.i have 4 drives in my computer.but in drive D there is a lot of data in it ,but it is hidden .when i check my drive D there is nothing in it .when i check the property of that drive there is 27gb used.i have scan my computer with latest anti-viuse.but in vain.who can solve my problem .how i can remove this problem tell me i will be ever than ful to u.
My Mail id is :- jannat_xi@yahoo.com (or) dextrous08@gmail.com.if any 1 know any this obut it then e-mail .Iwlll be ever thank full to u .