Don't delete those other LW folders!!
Reinstall LW. Make sure to use the offline installer (when you click to download & a box pops up, ignore it. You'll see a link to download using the offline installer, inside an orange box on the download page...use that offline installer). Install that new version, it'll automatically remove the one you're using now. Once it's installed, restart your computer & open LW. Give it a couple of minutes...see if the new version will connect. If it doesn't, go & look again for that LimeWire folder. It should definitely be there in the Application Data folder.
For your port forwarding: Once you've opened your browser, type that IP (192.168.1.254) into the address bar. Check the screenshot here
That IP is just the default one for your router (mine's 192.168.1.1...they're different for different routers), when you type that into the address bar & hit enter, your router's pages should open.