Click Start > Search and look for a file called winword.exe.
If the file's not there then Microsoft Word wasn't installed when the XP operating system was put onto the new drive. (Word isn't actually part of XP itself).
If the file's there, double-click on it.
If Word then opens normally your problem is simply with a dodgy shortcut (which is trying to find and open Microsoft FrontPage instead of Microsoft Word). Right-click on winword.exe and use the option to create a new desktop shortcut.
If Word fails to open when you double-click on winword.exe then Word has failed to install properly.