Is there any way I can take backup of my shnd wallet in external hard drive so as to protect the same?
you can copy the entire data directory,
or just the wallet.dat from the data directory
the entire directory may be helpful for later syncing as it contains a copy of the entire current blockchain, or it may be overkill.
in most cases the wallet.dat is sufficient.
By dat directory you mean the whole appsdata roaming stronghands folder? or so wallet.dat is all that's needed? so if i download stronghands on another comp and paste that in my current wallet will come up? Is each .dat file unique?