Wifi Router: Unable to change from WPA-PSK to WPA/WPA2

I am using a TP-Link TL-WR340G wifi router at my home. In order to secure the network i am using the security type as "WPA-PSK/WPA2-PSK" and in phrase i have given as "abcdefgh" as the PSK Passphrase. So when i had first time connected to the wifi router i was asked this phrase and it got connected. Now somehow it has got saved so now as i turn on the wifi on my laptop it automatically is connected to the network.
Now i need to connect my media player to internet using this wifi router and media player can (i presume) work only with WPA and WEP security options. So i did the following

1. I tried to change this option to WPA/WPA2 in the router settings by going to it homepage (192.168.1.1).

2. This i did by connecting the LAN cable to router (and not over wifi). The settings got saved and i got "network cable uplugged" and then network came back. The router resetted / rebooted.

3. Now i disconnected the LAN cable and started connecting through wifi and it gave an error saying "windows cannot find the security certificate....." and in the place where i see all the wireless devices around me for this router instead of showing "acquiring network address" or "connected" it is showing as "validating identity".

4. This goes on an on and so i again put LAN cable and revert to old settings of security option and it works again.

How can i change this to WPA/WPA2 and in that what is that Radius sever ip. I have no clue about that I just gave some random IP (100.1.1.1) and gave a radius password.

Also can i use WEP and i that case what security option i should select (automatic, open system, shared key) and what are those four rows of WEP keys ???

Just reset the device

^^ The changes are happening at the router level and they get saved too. It is the laptop which is no able to connect after the security type is changed. I suppose all references of the router (preferred network etc) will have to be removed from laptop. Where all i have to remove them from ?

remove wireless network from network settings in control panel