On and off the network

I have a computer in my department that is being used as a digital xray server to store photos on and the system will not show up on the network about once every week.The network card is a Realtekrtl3189 and the system is windows xp.I updated the drivers for the NIC and still this happnens.The system is updated with all the latest windows updates and everything,I’ve changed out the cables also and i still don’t know what could be causing this.Any help would be appreciated.