Thank's to Coulterp, I managed to turn the Netgear WGR614 v9 wireless router into an Access Point for a client:
Configure the IP address of the secondary router (the WGR614) to be in
the same subnet as the primary router (the Belkin), but out of the
range of the DHCP server in the primary router. For instance if the
DHCP server of the primary router issues addresses 192.168.0.2 -
192.168.0.100, then assign the secondary router 192.168.0.254 as it's
IP address.
Disable the DHCP server in the secondary router (WGR614).
Connect
from the primary router's LAN port to one of the LAN ports on the
secondary router. If there is no uplink port and neither of the routers
had auto-sensing ports, your would use a cross-over cable but that will
not be necessary here as the Netgear has auto-sensing ports, so a
normal straight-through CAT5 cable is fine. Leave the WAN port of the
secondary router (WGR614) unconnected!
Setup the wireless section on the WGR614 just the way you would if it was the primary router.