it took me a while but here it goes. First of all what 2500 do you have? The config I am giving you works for my 2514 router. E0 is connected to cable and E1 is connected to my lan.Perform a "ipconfig /all" on your computer and jot down the following: computer name, default gateway,mac -address, dns server.
E0
mac-addresss xxxx.xxxx.xxxx (mac-add from computer)
ip address dhcp client-id ethernet 0 hostname "abcd" (computer name)
ip nat outside
E1
ip address 192.100.100.1 255.255.255.0
ip nat outside
access-list 1 permit 192.168.100.0 0.0.0.255
ip nat inside source list 1 interface ethernet 0 overload
ip route 0.0.0.0 0.0.0.0 ethernet 0
now once you hook up your router to cable you will have to use a different ethernet card for your computer since you gave that mac address to the router's interface E0.
That should do it.