You're obviously using a PC and I know that these are completely different to Macs, but this is what I'd do on a Mac given what you have said.
- Uninstall/trash everything to do with the router - preferences and all.
- Restart
- Try to connect with the etherenet cable to establish that the machine can indeed connect.
- Now re-install the router's software and go through the set up wizard
- This IP address for the router can usually be found on the bottom of the unit
- Set your new WEP password and name the network
- Restart all devices in line - the cable modem, the router and the laptop - this is important!!
- Theoretically the laptop should now connect!!