Hi 1. If you are using a hub replacing that with switches will reduce the delay in case many users simultaneously access the network copy files etc.
2. Firewalls and antivirus softwares cause network delay. If u have some AV of firewalls installed uninstall it and check the speed. If u find improvement u can install a better AV although that will cause delay to some extent.
3. Virus / malwares cause network delay. Reinstall the OS use some updated AV and check it.
4. If you mean delay in Internet connectivity then you have to go for greater bandwidth.
01. A Single Hub with in the network of Switches can easily cause network delays as it broadcasts the packets. 02. Extensive cable lengths may also cause network delays