I recently purchased the Belkin PLAY N600 router to create a private network for my home theatre setup.
I have a primary home network 192.168.0.x (NetGear) which I use for all my computing needs. I extended a network cable to my Home theatre area and plugged in the N600 router. After this, I attached a USB external hard drive to the router and it works great. I can see it from the 192.168.2.x home theatre network (Belkin).
I would like to expose the USB hard drive hooked to the Belkin Router to my primary network so that I can copy over my music and pictures without having to physically move the hard driveonto a PC connected to the primary domain.
The Belkin router has a DMZ function which exposes an IP on its internal (192.168.2.x)network to the external (192.168.0.103) network.
Is it feasible to expose the USB drive to my primary home network?
Depends if you can map a device that is connected directly to the router to a IP. If this was a network storage device it would work. In this case you are trying to put the router itself in the DMZ.
Unless you have a security concern in your house I would connect the cable to your new routers LAN port rather than the WAN and disable DHCP or put the router in bridge mode. This would make you new router a wireless switch and all your IP would be on the 192.168.0.x net.