There is a 32bit related bug that prevents the Sentry app from running launching on Windows 7 32bit machines.
Find and launch the Sentry.exe in the "win" folder instead.
You can do this by navigating to the drive letter that is your DataLocker Sentry (usually D drive or E drive or F drive)
Navigate to the appropriate drive and then open it and navigate to the WIN folder.
Next, open the WIN folder and find the sentry.exe file (in this example it is Sentry3.exe)
That should bring up your DataLocker Sentry Login so that you can log into your device.
You can now log into the drive and then open the folder with your files in it. (In my case it assigns drive G to my encrypted folder/files) by clicking "My Files (G:\)