Computer randomly connects and disconnects from network

[wardy22]

my network looks like this: the modem connects to a D-Link DIR-655 which connects to a computer (Vista) and a switch, the switch then connects to another computer (Win7) and an xbox.

the problem is that the vista computer will randomly connect and disconnect from the internet/network. The vista computer also generally runs very slow on the internet. The Win7 computer runs perfectly and there is never an issue, so I'm wondering if the problem has to do with the vista computer not being connected to the switch?

It is not an issue with the router, I have tried two already and the same issue occurs.

the vista computer is running with a Gigabyte GA-EP45-UD3R which has a Realtek 8111C LAN chipset.

 

[damian86]

Why are you using a switch? Just use a router, your problem will go away

 

[wardy22]

I have the vista computer next to the modem and router in one room, then the switch, Win7 computer and Xbox in another room.

Why is the switch causing a problem?

 

[wardy22]

This is a pretty good picture of how my network is set up, the difference is the router only goes to one computer and the switch goes to a computer and an xbox.

 

[wardy22]

Could it be a problem with vista or the computer in general and not the network?

if anybody has any advice it would be greatly appreciated.

 

[wardy22]

The problem is getting pretty bad. No scans are picking up any viruses on any computer on the network but yet this one computer randomly runs unusually slow. pPease help!