Computer Info: Windows XP Service Pack 1, P4 512 ram. Belkin Pre-N
wireless network card and D-link network card.

Belkin Pre-N wireless card connects to a Linksys network which
provides internet.  D-Link network card connects to a Wired network to
share files (NOT ASSOCIATED WITH THE LINKSYS ROUTER OR THE COMPUTER
CONNECTED TO THE LINKSYS ROUTER).

I can't run both the networks at the same time, I can run them
indivisually. Basically I would need disable one of the network to run
the other one.  When both networks are connected only the Wired
network works.

Can I get detail answer, I am beginner at networking (I can do basic
stuff, but also can follow steps to do more complicated stuff).