What does IP Configuration 192.168.1.100 in use by 00:06:25:2f:29:37, DHCP Server 192

I'm new to this type of thing, but am confused by an error message I keep getting: "IP Configuration Error 192.168.1.100 in use by 00:06:25:2f:29:37, DHCP Server 192.168.1.1" I have an I-mac and we also have a windows laptop (soon to be replaced by a mac) hooked up to a router. The mac is hooked to the router. I don't know if this is related to the above error message, but we have to unplug the router and plug it back in at least 5 times a day because the internet just gets disconnected (we use cable). Any ideas out there? If so, please speak very layman terms as I am not a techy.

Thanks so much for you "techys".
Elle

means that something else on your network has the IP address your mac is trying to grab. Go into network preferences, Advanced and renew DHCP lease.