Hey hope you can all help me again

basically got a new laptop and its wireless enabled.
originally set up my router with an older laptop and i acessed the router via a utility program.
Now that laptop is gone .. and the new one dos not have this utility.i did have my security wep number written down on a bit of paper

as i used it to set up this laptop
I've lost it and i need the code for another laptop and i have no idea how to access the router now to get the code.
I know last time i acessed the router via the net using an ip number?? to acess the router directly..
anyone help??