Look at the following screen capture:
Mass_rename_test1.png
First add a couple of files to the main screen of the File Tool, select those files and then start the Mass Renamer tool.
The original names of the files should been shown under "Sample" > "Current" on the Mass File Renamer screen.
Click on the tab "Fixed text". "Add fixed text" should be shown with the box "Text" (see red rectangle on the screen capture).
In that text box you are able to write text and then enter that text under "Filename" when clicking on the button "Add".
The new filename is shown in the box next to "New".
If your screen looks different, please make a screen capture and add it to a following post. You can upload attachments by clicking on the tab "Upload attachment" at the bottom of the forum screen (next to "Options").
If the "Add fixed text" with the "Text" box do not appear on your screen, then it could be an issue for OS Vista 64bit.
When you click on the other tabs at the top of the screen, i.e. "Counter", "Copy data from original name", "Convert case" and "Find and replace", what happens? Do you see new boxes appearing on the screen or does that screen remain "virginal"? If nothing pops up then it's an issue.