1. Right click on Start and select Search. Enter Normal.dot in the seach box and select drive C in the "Look in:" box. [Note: I'm assuming your Normal.dot file is on drive C. If you have a paritioned drive or multiple hard drives and the file is not on C, select the appropriate drive letter or just select My Computer to cover all drives/partitions.]
2. Once found, right click on the file and select Rename. Type Normal.old in the Rename box.
3. Now, start Word. Is the grid gone?
Edit: Normal.dot is a template that stores the settings in effect when a new/blank Word document is opened. For a new installation of Office, it will be the standard, default settings. If the user has modified toolbars, created macros, changes settings under Tools, Options, etc, it stores those changes.
The purpose of the renaming procedure is to force Word to create a new Normal.dot; it will be the default template installed when Office is initially installed.