Re: when i install the windows phone tp will it forget my wifi passwords?
You may want to obtain those passwords before installing the preview. If it's your home WiFi, the password is usually located on a label on the WiFi router itself.
Re: when i install the windows phone tp will it forget my wifi passwords?
If you also have a pc and sync settings between your phone and PC these wifi networks and passwords will also show up on your PC. And here you can see (make them visible) the passwords.