2 ethernet card, slow or variable internet speed

[SkinnyV]

Hi,

I have an issue that si driving me nut since 3 days. Here's the situation:

I have a PC with 2 netword card, 1 connected to a router with internet access and the other connected to another router to get access to a private lan that shouldn't have any access to the net. i have set everything up as follow:

NIC #1:
IP: 192.168.1.6
subnet: 255.255.255.128
Gateway: 192.168.1.1 (internet router)
DNS: 192.168.1.1
Router IP: 192.168.1.1

NIC #2: (set to DHCP, heres the setting assigned by router)
IP: 192.168.0.2
Subnet: 255.255.255.0
Gateway: 192.168.0.99
DNS: 192.168.0.99
Router IP: 192.168.0.99

Everything seem to be working fine except that my internet connection on NIC #1 is not as fast as it was before when I do a speed test, while all the other pc (wireless) connected to that same router and connection register the usual speed when I test the bandwitdh.

Is there something i did wrong or that I overlooked? It's obviously not the router or internet since the 2 laptos connected to it score the regular speed on speedtest...

The reason of that setup is I need to connect my xbox 360 to my network to access my networked storage for video streaming without it have any chance of ever connecting to the net so thats the best system I could come up with.

Sometime I do the speed test and i can't even get 1 mb while i usualy get 7.2 mb, then when I try later during the day I get 6.5mb. If I use the the other nic for streaming movie sometime I can't even conenct to the net...

Any help you guys can give me would be appreciated as it's driving me crazy.

Thanks!