Is there a simple, free way to detect if a CAT5 cable has an active
internet.

The problem is that the two desktops running Windows 7 PRO do not show a
direct CAT5 connection, they just show a WiFi connection. Plugging in
the CAT5 cable does nothing.

Either something killed the desktops ability to access the CAT5
connections or the CAT5 cable is dead.

It is an AT&T FIOS WiFi router.