lamarckxerox wrote:Thankyou for your responses... XP is using the default gateway, and rpi is on 192.168.43.1. If it is relevant I had to set a static IP address on the XP box to get ethernet to work.
It isn't a router thing as I don't have one!
How are they connected together? You mention using 3g for the internet, the most you can do with the pi and the XP box each with one place to put ethernet cables is to connect each other. If the XP box is connected to the 3g with wifi and then the rpi is connected to the XP box with ethernet, this is a more complicated network than usual and the automatic configuration efforts of all the machines will probably not work. I don't know why they worked for a period, which I think you said earlier.
I just went back and read some of the previous stuff. Since you are mixing wifi and ethernet, I think you need to either do it in a different way or configure the XP box to share internet. As I recall, the included stuff for that is pretty poor but it can work. It might be limited to certain subnets, I am a bit hazy in recall here.
But since your phone is putting out wifi, why can't the pi just get its own wifi dongle and connect that way? Why can't the XP dongle go on the pi and then XP connects through the pi ethernet to wifi and then the 3g? The XP box does have an external wifi dongle, right?
The reason for thinking about doing it this way is because you are more likely to get success using the Linux box as a router than the old Windows one, I mean with each system's built in software. Also, people won't be telling you so often to erase XP and put Debian on it which you don't want to do because, you know, you want to be able to run your Windows programs.