It seems there is no TL-WN320G product on TP-LINK website even discontinued product.

Read your story and feel confused. Do you want to use TL-WN721N replace your ADSL router? If my guess is right, it's so strange and I don't think it can meet your needs...

it's a long story... firstly, you may refer to the following link to check whether the driver is installed successfully or not. http://www.tp-link.com/en/article/?faqid=284 then, if it's working...

it seems that it can't support WEP security...

You may try the following link: http://www.tp-link.com/en/article/?faqid=306

when you disconnect wifi, please refer to the following link to check whether the driver is working or not.: http://www.tp-link.com/en/article/?faqid=284 If it's working properly, you may try to set...