Terminal Server Client Problem!

Our NT4.0 Terminal Server has 2 partitions – a C: drive and a D: drive. When a client used to logon and open Explorer, they could view the C: drive, the D: drive and Network Neighbourhood.

But now, something appears to have gone wrong because when they logon and open Explorer all they can see is the C: drive. This is causing problems because the company files are stored on the D: drive – they need to be able to access it but they can’t. Mapping the network drive doesn’t appear to work either. What do I do? Please Help?