How have you tried to connect the XBox to the router or PC? Wired only I presume and to a port which is designated as being in the DMZ (De-Militarised Zone)? Please expand on the configurations you have tried and the results.
Form other threads here, you would have read that if your PC does not get assigned a 192.xxx.x.xx IP address by your router, its because the wireless or wired connection has not been made successfully.
Have you got data encryption set on? WEP or WPA? Router model?