I have no idea about your Silvercrest DVD player but have you tried going to google put in the model of the player and ask about installing a usb hardrive.
Ask something like this on google
Model number XXXX external hardrive not Recognized when plugged into the usb port
Not sure you will find anything but worth a try.
You also should provided the model of the player and hard drive in your post it would help
I went to google and searched (Silvercrest DVD player external hardrive)
There are post there about the formating of the hard drive having to be FAt32.
Reads some of the things on google and see if that helps.