cannot access router

> My problem, I just cannot access the WAC730.

   When you do what, exactly?  "cannot" is not a useful problem
description.  It does not say what you did.  It does not say what
happened when you did it.  As usual, showing actual actions with their
actual results (error messages, LED indicators, ...) can be more helpful
than vague descriptions or interpretations.

> Trying to disable the DHCP-feature on my DELL, setting a fixed IP-adress
> and the attempt to access the WAC with the 192.168.0.100 address did not
> work either. It just leads to a sytem error automatically fixed by my
> Windows 7, x64 , SP1 operating system.

   Which "a fixed IP-adress"?  I don't know what "leads to a sytem error
automatically fixed" means.  See "not a useful problem description",
above.

> The WAC is not recognized by my system.

   I don't know what that means, either.

   Visit http://netgear.com/support , put in your actual model number,
and look for Documentation.  Get the User Manual.  Read.  When I did
that, I found the following in the "Initial Setup" chapter:

      The default IP address of your access point is 192.168.0.100.

      By default, the access point functions as a DHCP client. If the
      access point is installed in a network that includes a DHCP
      server, the IP address of the access point is issued by the DHCP
      server.  [...]

   As I read that, if the WAC730 is connected to your computer, but not
to your LAN, then it should have its default IP address,
"192.168.0.100" (and, so, to talk to the WAC730, your computer must have
an address on that subnet).  If you connect the WAC730 to your LAN, and
it talks to your DHCP server, then it should get its (non-default) IP
address from that (and you'd probably need to talk to the DHCP server to
see what it gave to the WAC730).