Our Internet is cable and we use a modem supplied by our ISP. Recently I have been given a Cisco 857W router. Is there any advantage in adding this router to the existing system? I am hoping to have more control over access by other users on the network. The existing modem does not allow this. There are 3 desk tops and 2 wireless laptops on this network and I know nothing about Cisco routers.

I couldn't tell you much about that specific router, but what kind of "more control" are you looking for exactly?

Having contacted Cisco support apparently that model is not compatible with Cable. The control I am looking for is access restriction for certain users.

By time, or just to certain websites? I use OpenWrt on a $50 WRT54GL and it can do all that, if you're comfortable with shell scripting and iptables.

Tomato and DD-WRT can probably do it as well, if you want a GUI option.