Here's something you could try:
Connect both the hard drives you want to be docked to the docking station, then plug it into your laptop like normal. Then go into the Device Management console (if you know how) and find the entry pertaining to the docking station, although I'm not sure what category this would come under. Perhaps 'Storage controllers' or similar?
Once you've found said entry, right-click on it and select 'Uninstall'. Then you can do one of two things (with the docking station still connected): either click the button at the top entitled 'Scan for hardware changes', or restart the computer. Either way Windows should try to re-install the drivers for the docking station, and then accordingly mount the drives and auto-assign each drive a drive letter for access under 'My Computer' (or 'Computer' under Vista or 7).
Hope this helps.