403 Error, please help

[RomeoX1000]

Okay, so here's the deal. I've been using a Linksys wireless router to use my PC (running IE) and also my chick's Macbook running Safari. Recently had to disconnect my router for various reasons, only to realize that when I unplugged it, my internet was still working for both my chick's computer and mine. Due to the similarity in names between the two networks I had been piggybacking on someone else's signal for about 2 years without realizing it (honestly, completely by accident.) Finally realized and went to setup my own network again, with original name this time and PSK encryption. Connected to it with my PC, no problem. Went to connect my chick's Laptop to it, located the network with her comp, typed in the PSK, opened Safari, problem. Error 403 Forbidden. Every website that I've tried, except Comcast.com, which is our ISP. Any ideas what I can do to resolve this? By the way, I'm not completely computer savvy, so layman's terms would be appreciated. Thanks in advance!