My Book World Edition (Ethernet) + Airport Express + Verizon Westell Router

My configuration pre My Book Network Hard Drive Ethernet was my Verizon Westell router is plugged into my Airport Express and I get wireless internet through my Airport Express along with being able to stream itunes to my JVC stereo and use my printer.

Now I want to throw my WD Network Hard Drive Ethernet into the mix and be able to access it with my Airport Express also.

So far I’ve managed to have it plugged directly into my Westell router but I have to switch back and forth between the Westell connection and the Airport Express connection to be able to access the drive.

I bought a Netgear 5 port switcher thinking that would help but it didn’t solve the problem or I was mixing a key factor which I don’t know.

Can someone here help me shine some light on how to get the My Book Ethernet to be accessible via Airport Express versus having to switch between connections, Please?

I have a MacBookPro 10.5 running Leopard