cable modem and wireless setup

Hey guys im having some trouble getting the internet and a wireless connection to some laptops.

I have a motorolo cable modem which is connected to a D-link Di-524 wireless router's WAN port. Then in port one of the D-Link router im going into an ethernet card at the back of the desktop computer.

Cable------------ -------- into desktop Ethernet
- WAN PORT - (DLink wireless card)
- - -
- ---D-link Router-----------
Dlinks Ethernet Port


The desktop computer before was running an adhoc so i still have a D-link wireless card in the desktop computer. Everything is on infrastructure all SSIDS being broadcasted by the router.

The cable modem IP range is different to what is whats being broadcasted on the router does that make any difference?