Installing Windows 7 on first partition restrict access to 2nd partition

I have two partition on my hard drive that is Drive C and Drive D. I have installed the Windows 7 on C drive and after installing this, I found that the Drive D is not accessible. I can see the both the drives but that is not accessible. Some of my friends told me to format the D drive and that will be accessible again but I have a lot of materials saved in that and I do not wish to lose those data from my drive. Can somebody tell me any alternate solution for this? Thank you in advance for replying.

This is seemed to be problem with the permission on that drive and you are not having proper permission to access that drive. I think that the permission to the section where the root for the file system lying on D: just have identities as of the old Windows installation. Also, you can check by right clicking on D: drive and then select Security.

Just restart the Windows and after that try to run the scandisk on that partition to see if that can help you in any way.