connect to the routers ip as your gateway and not the local machine.
your ISP probably uses DHCP to assign IP addresses so leave DHCP enabled on the router. set a static ip locally for the windows box & use a netmask 255.255.255.0

start a windows command tool from the start>run type cmd and click on "okay"

type 'ipconfig /all > ipconfig.txt' and hit return

this will redirect the output of the command to a file in the local directory called ipconfig.txt.

open ipconfig.txt with an editor and post the content of the file back to us so
we can see what you have going on.

also, post a general router configuration if using one.