Ethernet Connection To Belkin Router

When I commenced using my MacPro last year I found it to be immediatelyin touch via ethernet with the internet through my Belkin together with my G4 and a PC laptop, the latter using WIFI. Recently, I've had a problem with my connections and partly finalised matters by going through the many cookies which had arrived on my G4 in my absence from home through others' use.... (and they won't be using it anymore!) I say partly finalised because the connection with my G5, which had appeared so easily when I first installed has now disappeared and, despite my looking at the settings and trying to rearrange them, I am failing dismally so I can't use it to download future improvements from Apple. Most important for things like FCP etc.

My ISP does not provide an address for the router. It is through DHCP auto. I'm not sure how to obtain it again for the G5 and the settings show that it is locked onto a fixed TCIP reading which I can't open and which doesn't work... ! When I try settings similar to my other computers with a changed address to try and match it, there's no sign of acceptance.

Does anyone here know the remedy ? T.I.A.

Ron