after i setup new server and configuared active directory, every think work fine
but when i power on more than 3 workstation pc's the network become too slow and some times i cant reach my server
whats the problem?
You may want to investigate this by looking at your network equipment. For example are you using hubs or switches? Do you see any indication there that there may be a problem. Or take a packet capture. Do you see abnormalities in the traffic patterns for example too many broadcasts, unnecessary protocols, retransmission?
JorgeM is correct that you need to look at the network. You need to look at the speed of the NIC Cards in your computers and the speed of the hubs, switches and routers on your network. Also look at the quality of the cable you are using (if your using mostly wireless network devices then you need to move to a wired network for at least the server.) Also how are you assigning IP addresses (is the domian controller handeling it?).