Windows 7 Access denied D drive. How to get access back?

Always remember in the NTFS world Deny flags always over ride Allow flags.

So if you have a folder/driver and add Everyoneeny permission you've just locked every account out.

You can try running a command prompt as administrator, and to "takeown /r D:\", or right click the drive, properties, and take ownership back then set permissions. Hopefully you did not encrypt the drive...