Some of your Word files may be corrupt or the Word file you are trying to open.
You can try to repair MS Word and the file mso9.dll by doing the following actions:
1. Search for mso9.dll in in your computer using the Search option from Start.
2. Rename it to mso9.old, and then press ENTER.
3. Also do that for Winword.exe file and rename it to Winword.old.
4. Go to Control panel-> Add/Remove Programs find MS Word and click Repair.
5. On the Install/Uninstall tab, click Microsoft Office 2000 in the list of installed programs, and then click Add/Remove.
6. In the Maintenance Mode dialog box, click Repair Office.
7. In the Reinstall or Repair dialog box, click Repair errors in my Office installation, and then click Finish.
We advice you to try the Word file on another computer. If the error is the same it means that the Word file is corrupt and you should try to recover it because is damaged.