NAT settings, Xbox Live?

I'm using and WNDR3300 router, and a Windows Vista OS (awful, I know, wasn't my choice). My NAT settings are apparently "moderate". I've tried opening the Upnp settings, opening the NAT filter, and using a DMZ. I access Xbox Live via using my computer as a gateway, which has a wireless adapter in it, connecting to the router downstairs. I can't use port forwarding because my xbox IP has a zero near end (192.168.0.x) rather than a one (192.168.1.x). It has the first three numbers (in the port forwarding router settings) set by default, only allowing me to change the last digits only (where the .x is). Any time I try to change IP addresses on the LAN and/or Xbox so it has a standard IP (192.168.1.1 or 2), it disables the entire internet connection. I've also tried changing my upnp hop settings, etc. to respond to connections faster to no avail. Help would be appreciated!