If you start word with the /A command does it work? This loads word in a safemode. If this works then chances are you have registry corruption
Does this workaround work for you either:
1. Start Outlook, and then click Options on the Tools menu.
2. On the Mail Format tab, click HTML in the Send in this message format box, and then click OK.
3. Quit Outlook.
4, Open word and try again.
If either of these options fixes it (albeit temporarily) do this to solve your issue:
1. Click Start, and then click Run.
2. In the Run dialog box, type regedit, and then click OK.
3. In Registry Editor, navigate to the following registry key:
4. On the Registry menu, click Export Registry File.
5. In the Export Registry File dialog box, select Desktop in the Save in box, and then type OfficeKeyOld in the File name box. Under Export range, click Selected branch, and then click Save.
6. On the Edit menu, click Delete. Click Yes to confirm the deletion.
7. On the Registry menu, click Exit.
8. Click Start, point to Settings, and then click Control Panel.
NOTE: In Microsoft Windows XP, click Control Panel directly on the Start menu.
9. Double-click Add/Remove Programs.
10. In the list of currently installed programs, click Microsoft Office 2000, and then click Add/Remove.
11. In the Office Maintenance Mode Wizard, click Repair Office, click Repair errors in my Office installation, and then click Finish.