Let's Begin:

In order to recover your data, please follow the steps below:

1a) The easiest way to do this is to recover your files from your computer at their orignol location using free data recovery tools here are some examples:

http://www.winundelete.com/?rid=google&kid=wu0406
http://www.recovermyfiles.com/
http://www.ontrack.com/software/ 

1b)If you cannot recover the source files (original location on the computer) you will need to recover the Data folder on the root of your usb device. (E.G The "WDsyncData" folder) using the same software above.

Note: If you did not use an encrypted profile this is all you need to do you should find your files with the recovered  "Wd Sync Data" folder.

Recovery of Encrypted data:
2b)Once you have recovered your profile folder (the "Wd Sync Data" folder). There is a recovery tool that can recover data that WDSync doesn't detect any more. What it really does is decrypt those funny AES files but you will need you password. If you have lost the password it can be recovered but unfortunately I cant tell you how to do that here.

This tool is available at this address: 
http://www.dmailer.org/download/DataRecoveryTool.zip

3b)When you have downloaded it, here are the steps to use it:
1. Launch it and go to "Profiles->Scan directory"
2. Select your "WD Sync Data" folder containing your synchronized data. You should see all your profiles being listed.
3. Select the profile you wish to synchronize and click "SaveAllTo"
4. Choose the destination folder.
All your files from your profile will be recovered in his directory. Please note that this tool is not able to recover file names; you will need to rename your files manually.
Please let us know if you are able to recover your data with this tool.

DIR STRUCTURE
WDSyncData My profile Data
and in the Data directory
Sync4.0.deposit (with all your Outlook emails you want to retrieve)
Sync4.0.option
Sync4.0.db

Renaming the files:
4b) If you need help to renam your file and find their extension type you can use a free too TRIAD (http://mark0.net/soft-trid-e.html).

Download the software (http://mark0.net/download/trid_w32.zip) and the definition (http://mark0.net/download/triddefs.zip).
Unzip both package, copy the “TrIDDefs.trd” to the same folder as “TrID.exe”.
Open a command line (via Start/Execute TYPE= “cmd”) Navigate to the folder where “TrID.exe” is and use the command:

trid "%DRIVE_LETTER%...%RESTORE_FOLDER%*" -ae -w

e.g.: trid "C:usersjohndoerecoverdata*" -ae -w
(where “recoverdata” contains all your restored files)

The process should begin to check files. A percentage will be display behind each file to indicate the percentage of probability that the file type is the good one.

At the end of the process you should be prompted to press a key.
Just before, you will see the numbers of files renamed by the app. If this number is less than the files numbers you have in your folder, it's because some files have not been identified by TrID. You should check them manually.
All other files have been renamed and with the detected extension

Please note that the Dmailer Sync range has been discontinued and support is no longer provided. To stop this from happening again and various crashes upgrade to Dmailer Sync V9.

Support:
If you have any questions or have any problems you can contacting me for Dmailer Sync Support Here