The last person's suggestion won't work if you had to put static IP information in. I work in internet tech support and we generally recommend that our customer's call their router's tech support number because they can look up the specific model you have and direct you through it so you don't have to put information back in or set it up all over again.
Typically if the manufacturer sets it to something easy. 0000 or 1234. Etc. If these dont work use the reset button. Hold it down for approx 20 secs. Some reset buttons are needle pinpoint size and recessed in a hole.