Update download is a disc image file. Don't have that capability on my computer.

> Model: R7500|Nighthawk X4 AC2350 Smart WiFi Router

   R7500 or R7500v2?  Look at the product label.  Current firmware
version?

> Update download is a disc image file. [...]

   No, it's not.

> [...] Don't have that capability on my computer.

   Which "that capability"?  What is your "my computer"?  Are you doing
some (secret) thing which gives you some (secret) error message?

   If your problem report were any more terse, then it might be
_entirely_ useless.

   "Don't have that capability" 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 (commands) with their actual
results (error messages, LED indicators, ...) can be more helpful than
vague descriptions or interpretations.

   What, exactly, are you trying to do?  Load some firmware image into
your router somehow?

   The firmware image file for an R7500[v2] router has a file type of
".img", but it's not a "disc image" file; it's a firmware image file,
and the (unspecified) operating system of your (unspecified) "my
computer" does not recognize its contents when it tries to do whatever
it might normally do with a file typed as ".img", if you ask that OS to
"open" that file.

   Fortunately, your (unspecified) "my computer" does not need to know
anything about this kind of ".img" file for you to load it into your
router.  In general:

   Visit http://netgear.com/support , put in your (actual) model number,
and look for Downloads.  (For older versions, under Firmware and
Software Downloads, look for "View Previous Versions".)  Find the
kit(s).  Download the kit(s) you want.  Read the "Release Notes" file
for instructions.

   Recently, Netgear has stopped including actual instructions in its
firmware "Release Notes" files, so all you may see there is a hint like:

      To update your router's firmware, follow the instructions in your
      router's user manual.

   In that case, visit http://netgear.com/support , put in your (actual)
model number, and look for Documentation.  Get the User Manual.  Look
for "firmware" and/or "update" for the details.  (Which would have been
a good first step, in any case.)

It is not a disk image, it is an .img file.

To update your router follow the usual instructions:

How do I manually upgrade firmware to my NETGEAR router? | Answer | NETGEAR Support

At step 8, tell it to look for your .img file.

You should also find these instructions in the manual for your R7500.

>>> R7500 | Product | Support | NETGEAR <<<