Belkin Wireless G Router F5D7230-4 MTU cannot be set

Setting the NIC card to 1500 will NOT change anything at all if your router is set differently. I have the same router and there is no way I can change the mtu that I can find. Speedguide says my mtu is 1492, but I do not have a dsl line, I have cox cable. My connection is manually set for 1500, but the router appears to be overriding that, even though it's set for dynamic, not PPPoE. I'm running Vista 64 without autotuning.