Well, your setup is pretty messed up.
Why are you running the 192.168.0.0/27 network on BOTH sides of your PC1? It looks like you have two firewalls running. One is the Internet Connection Sharing on your PC and the other is on your router. That's a lot of protection.
When the xbox tries to go to 192.168.0.3 it compares it's own address and subnet mask of 192.168.0.27/27 and determines that PC2 is on the same subnet. The problem is it's NOT on the same subnet - you have two subnets in your house that have the same address. So the xbox is just broadcasting for PC2 and ignoring your PC1 ICS, and not gettnig a reponse. I would also think that PC2 would be unable to connect to anything on the XBOX side of the network for the same reason.
What you should really do is dump that ICS software and just use your router - plug all three things into it. If you don't have enough ports or if your xbox/pc is in a different room, you can daisy chain another hub off of that cable and then your PC and xbox can share that connection via the hub.
MiteeThoR