Disappearing Folders

--- Personal,
I have a HD partitioned into 4. The folders in the D: partition "disappeared." Totaling 1.7 GB. There are still 8.3 GB unused.
Values ​​can be found by Properties. (Right mouse button).
I have installed on any PC program to hide files and folders.
With Speed ​​Disk (Norton Defragmenter) can observe the blocks referring to 1.8 GB but can not see the folders and files as often happens in other partitions.
I activated the defragmentation process and everything went without any problems, which reinforces the material is still there and intact.
I tried looking through DOS but the result is the same. The DIR command can not list anything.
Appreciate if anyone has a suggestion as to what may be happening. And, of course, how can normalize the situation.
Grateful

--- If your drive is not no mistake and no one formatted this drive, they gotta be there! Tenata the following go into folder options, views and show hidden files and folders may be hidden files q someone! --- Jah

you thought about the possibility of being a virus! ---

Is a strong suspicion!