how client can access serevr on wokgroup ??????

i have made simple network workgroup on my office by simply connecting them with switch and assigning unique ip to each other i have one server windows 2003 standard edition and server is only file server and application server my problem is that client is not able to accesss shared resources of server i have to access then what should i do?igives message that “you dont have sufficient permission on network plz contact to you network administrator” how can i overcome this problem on my network?