You do not state the version of Word you're using but shown below is the procedure for Word 2000. It should be basically the same for other versions except possibly 2002.
1. Close Word.
2. Click Start/Run.
3. Make sure Windows Explorer is set to "Show all files." In Windows 98 this option can be selected by enabling "Show all Files" in Start/Settings/Folder Options/View Tab/Files & Folders/Hidden files.
4. Click on Start/Find/Files or Folders. Type normal.dot in the Named box. The Look In box should read C:\
5. Delete the file(s) found.
6. Reopen Word. The file deleted will be rebuilt automatically to the default settings. If you have made changes to the normal.dot template file, such as macros, they will have to be re-entered.
A new normal.dot file will be around 24-26Kb. A normal.dot file that reaches a size of hundreds of Kbs will eventually cause problems.