I'm not able to select HDTV in TV settings??

[ericuf]

It's greyed out .... Why is that??

 

[real-o]

Not sure, but I think this is probably what you're talking about.

http://www.nintendo.com/consumer/systems/wii/en_la/settingsScreen.jsp#resolution

Please note that you must have the Wii Component Video Cables, and your TV must support 480p in order to enable it.