server 2003

help , new server 2003 set up but i think i have managed to change settings. taking ages to log on from client computers. believe it is dns problem but not sure what to do . can any one explain how i can try to sort this in step by step language. have internet access on all machines. have dchp configured on server management and dns but does not seem to be right. was hoping to set up remote access but as primary teacher who fell into ict am out of my depth. help !