Photoshop :: Unable To Edit Text In A Template

editing the text in a web page template that I downloaded from a free template web site. The page is .psd file, I opened it in photoshop ver 6, went on to those layers which are having text. the layers clearly denotes T , I double clicked on T but as per tutorial I read on a web site, the text is not highlighted or selected, instead the blinking cursor comes over that text and when i try to write something it overwrite the new text over the previous one and previous text is as it is as its before.

I also tried to edit the text by going on vertical tool bar, clicking the T button, and then double clicking on the required text but it also doesnt work. After going through couple of tutorial websites and reading it, I came to know that text layer might be rasterized, I checked in the main menu, the layer is not rasterized and clearly show the letter T.