CAN'T use Word as editor; open attachments; hyperlink

All of a sudden Outlook 2003 doesn't allow me to:

1. use Word as its editor
2. open attachments
3. hyperlink to the web

I have Windows XP and MS Office 2003. Both Word and Outlook are 2003.

I've used the 'detect and repair' button in Word. When I try it in Outlook I get a message: "msiexec.exe cannot be started"

The file msiexec.exe is on my computer in 4 places.

Something must have become corrupt by I have no idea what.

I have completely uninstalled MS Office 2003 and reinstalled it. I've tried things I've seen suggested on the web but haven't found exactly what I need.

I saw a suggestion about deleting a key in the registry but it was for Word 2007 and the exact key doesn't exist in my registry.

Can anyone help me? I've used this all successfully for several years until one day, all of a sudden it happened.