Forum Moderators: open
[edited by: tedster at 9:49 pm (utc) on Nov. 30, 2005]
[edit reason] remove specifics [/edit]
PSD stands for "photoshop document" - and if you need to edit it, then you need Photoshop to do the job correctly.
However, in all likelihood, you will only need an html editor (or even a basic text editor) and can make all the changes you need right in the html document. You can certainly change text this way, and even substitute a different image for one that is included in the original template.
People use all kinds of applications to edit HTML files, including basic text editors (such as Notepad) and more elaborate editors that give you the advantage of many extra tools, such as color coding for different elements within the html, to make the document easier to understand at a glance. Examples of more advanced and commonly used "html editors" would include EditPlus, HTMLKit, Netscape, Composer, and Macromedia's Homesite (my favorite).