ok first you need to make sure the mac adress is the same as your router
then check the gateway (needs to be the same)
then check the IP address
perhaps you need to make a virtual server on your router with the ports useually 8080 to 8090 (read the manual of the DVR)
in the DVR you need to set the permissions, password etc
then when you log on to the DVR via the pc viewer you need to put in the IP address at the top, then the port (probably 8090) then user name (probably Admin) then the password you put in the DVR......
hope this helps?