is the router a router+modem in one?
turn off everything computer-related
if you have a separate router and modem, turn your modem on. then wait a minute, and then turn your router on. then wait another minute, and then turn on your computer.
if you have a rouer+modem in one, just turn that on first then wait a minute.
works? if so, great!
not work? click start->run, and type "cmd" (without the quotes), and click ok.
now at the DOS prompt that's just opened up, type "ipconfig /all"
somewhere there it should tell you that your IP address is found by DHCP, and your IP address should be something like 192.168.1.2...