What did they have her do? Hopefully not install software,
that isn't necessary and only complicates things.
Generally speaking, adding a router might mean they need the
MAC address, and the router should mostly use the default
settings. It probably needs set to Dynamic IP address, and
to renew the IP forever (continually, or however it's
worded). If there are other Comcast-specific requirements
(not "windows thing" but general what-comcast-needs,
things), these should be very basic and available upon
request.
Has she tried only resetting the router? It does not make
sense that, if the modem plus computer worked fine, now the
modem would need reset while connected to the router in
addition to the router needing it, IF it actually needs
reset, or perhaps resetting it just does something more like
renew the IP #.
Have her make a list of any and all things on the router
that were changed. Compare that to the Comcast requirements
to connect- they need not know she even has a router, only
that with any broadband, their system will have specific
host requirements. Typically most now simplify matters and
only need the MAC address registered in a couple databases
(as I believe Comcast uses AT&T networks so there's the
second database).
Well "must" is relative, you're paying for the service and
along with that comes the tech support. Typically tech
support automatically assumes the user has a problem on
their end and advises a power-cycling of all equipment, and
sometimes that is a fair presumption. Other times, THEIR
network may have an outtage and the client may struggle and
it seems something works but the intermittent connection has
simple come back. She might also check to be sure the
router isn't overheating- being passively cooled it should
not be wedged into a tight place or hot area.
Practically all routers now have a HTML (web) interface
accessible by a browser (like IE or whatever...). The
manual should provide the IP # for this access, typically
it's something like 192.168.0.1. If that is entered into
the browser like a URL, for example;
http://192.168.0.1 , that should bring up the router login
screen where (hopefully no password is set or she remembers
it- the default password should be listed in the router
manual). In these router web pages there should be a log
that can be checked, perhaps a status feedback page and a
reboot option.
Likewise with the modem, often the modem menu is
http://192.168.100.1/
It too should have a status page, a log page, perhaps a
signal strength page and other various things depending on
what access level the ISP has allowed. Before rebooting
either of these pieces it would be good to try to isolate
whether either actually needed rebooted. The modem should
also have status LEDs on the front of it.
Modem downstream power level can be a problem, especially if
it gets near -15dBmv which is often considered a lower
threshold. Too many TVs, splitters, poor cabling in general
can cause poor signal and a signal booster often cannot be
used. We don't know her environment, whether house,
apartment or whatever but getting outside the physical
hardware on-premises, the physical cable and then the ISP's
equipment could also be a problem. Exterior parts age and
while is used to work ok, things like temperature changes
outside can degrade poor cable connections.
The only way to really isolate something like that is to
reattach it without the router. If the router does seem the
only thing causing the problem then recheck the settings,
possible even reset it (detailed in the manual, often a
reset button is held in for a period while it's turned on,
but check the manual for the specific procedure). After
resetting it, using the aforementioned router web page the
settings provided by Comcast can be re-entered.
With all the above I am assuming this always happens on the
hard-wired (ethernet) desktop as well as the laptop. If
only over wifi, it could simply be that the wifi signal has
interference from an outside source or even her notebook
network adapter is flaky. You did not mention how she might
have had wireless for the laptop prior to the wifi router so
we cannot be sure if only one or both systems have the
failed connection in either configuration (with and without
router).
