WNDR4500 port forwarding with fixed IP address

> [...] my WNDR4500 router.

   Plain WNDR4500, not v2 or v3?  Not really a "Cable Modems & Routers"
item, more of a plain-old router.  Is there a cable modem feeding this
thing?  Is that thing in a bridge mode, or will a user in the outside
world need to bore through two routers (cable modem+router and WNDR4500
router) to get to your Web server?

> One of my wired PCs has a local address of 10.0.0.7;

   So, some version of Windows?  Ok.  But you need to fix (make
constant) that address, because the port-forwarding rule will include a
target IP address, and if your PC address changes, any port-forwarding
rule which points to it will fail.  There are two ways to do that.  On
the router, you can reserve an address for it, perhaps under ADVANCED >
Setup > LAN Setup : Address Reservation.  Or, on the PC itself, you can
specify all the addresses manually, instead of using DHCP
("automatically").  Reserving an address for it on the router is
probably easier.  I generally shrink the DHCP pool ("Single/Start IP
Address" and "Finish IP Address", so that there are some addresses
outside the pool, and then I use those non-pool addresses for such
reservations.

> [...] I do not see any place on the Port Forwarding screen for
> entering a local address, unless I replace 10.0.0.7, [...]

   The router Web form should fill in the subnet parts, "10.0.0", and
you should fill in the host part, like, say, ".7", to get a whole
address like "10.0.0.7".

> I'd like, please, excru[c]iatingly detailed instructions for forwarding
> port 80 traffic to my 10.0.0. 7 PC, with or without a fixed IP address.

   If it's not fixed, then your PC may very well wander away to another
address the next time it or the router is rebooted.  You want it fixed,
one way or another.

> I'm not even sure what the difference is between a fixed and a dynamic
> IP address is in this context.

   A static address is one which the device knows on its own, without
asking anyone else.  In Windows, that's the "Use the following IP
address" choice.  (Using that requires you to know how to fill in all
those fields: IP address, Subnet mask, and Default gateway.

   A dynamic address is one which the device gets from a Dynamic Host
Configuration Protocol (DHCP) server (like your router).  (When the
device starts up, it broadcasts a "Help me!" message.  The DHCP server
responds with all the required data.)  In Windows, that's the "Obtain an
IP address automatically" choice.

   A static address is always fixed.  A dynamic address is fixed if the
DHCP server always responds (to a particular device) with the same data.
(The DCHP server can identify a particular device by its MAC address,
which is a hardware property.  Strictly speaking, that "Help me!"
message is really more like "Help me!  My MAC address is [for example]
11:22:33:44:55:66.")  If the DHCP server gets a request from an
unrecognized MAC address, then it pulls a free IP address out of its IP
address pool, and returns that.  If the DHCP server has a reserved IP
address for that MAC address, then it returns that.

   So, what I might do in your situation would be to shrink the DHCP
pool from (I assume) ".2" - ".254" (which is practically everything in
the subnet) to something like, say, ".2" - ".199".  That pool would
accommodate 198 devices, leaving ".200" - ".254" available for use as
reserved addresses.  (This kind of division makes it easy to distinguish
one set from the other in a list of attached devices, too.)

      ADVANCED > Setup > LAN Setup : Use Router as DHCP Server ...

   Then I'd reserve an address for the PC in the ".200" - ".254" range.
First, determine the MAC address of the (network interface of the) PC.
It should appear in the attached devices list:

      ADVANCED > Administration > Attached Devices

Then, choose a (new) address for the PC from the ".200" - ".254" range,
and reserve it:

      ADVANCED > Setup > LAN Setup : Address Reservation

For example, 10.0.0.207.  When this has been done, reboot the PC, and
verify that its address is the new one (10.0.0.207).  (If that failed,
then I'd shut down both the router and the PC, then restart both.)

   Finally, create the port-forwarding rule, with external port 80 being
forwarded to internal port 80 at IP address 10.0.0.207 (or whatever you
reserved for the PC).  On my D7000, "HTTP" is one of the predefined
services ("Service Name"), so this may be easy.

      ADVANCED > Advanced Setup > Port Forwarding / Port Triggering

   The post-final worry is whether your cable modem is also a router.
If so, then you may need to take further steps to make your new Web
server visible to the outside world.  However, in the mean time, if the
Web server on your PC is running, then you should be able to reach it at
the PC's LAN address (like http://10.00.0.207), or at the router's WAN
address:

      ADVANCED > Setup > Internet Setup : Internet IP Address


   If that much works, then look at that "Internet IP Address" of the
router.  If that's a 192.168.x.y, or 10.x.y.z, or some other private
(non-routable) address, then you'll need to decide how to deal with the
cable modem+router, so that it won't be blocking access from the outside
world.

   Sufficiently excruciating?