ADSL problem

[popy]

I've got two PCs (XP prof) LANned via an Ethernet switch.
I'm on broadband (ADSL). One PC connects with no problems. The other is behaving erratically. Sometimes it connects nicely and all works well for few weeks then all of a sudden it can't connect at all or if it does, the connection is weak. From time to time it begins connecting/disconnecting like mad and only if I disconnect the other PC it goes back to normal.
Both computers are well protected against viruses, malwares etc.
Any idea?
Thanks.

[mrjonnyevo]

you need to set up an ip address for each computer this can be done in network connection. youl need to know your ip dns number . email me and will go through process [email protected]

[popy]

It's all been done. As you can see from my question the problem is that one PC's connection behaves 'unpredictably'.
I appreciate your help, though.
Thanks mrjonnyevo.

[macspeedy]

its nothing to do with malware or viruses etc the digital signal is being split somehow perhaps the lan connection is the problem all goes on bus speeds on pc best to use a router it seems the pc you have directly connected takes up most of the bandwidth and the poor pc on the lan connection gets what the other doesnt use filtering through a slow ethernet port you havnt given any specs so i cant be sure really if your wiring up 2 pcs to the same dsl your best to use a router its designed to share the connection fairly does sound like the ethernet port needs upgrading on the main one

[popy]

Thanks for your answer mac. It's already been sorted out.