Disable start of Word when downloading files

Hello,


My iMac works just wonderfully for me. I do have one recurring irritation which is whenever i dowload an attachment from the internet (using Firefox 3.6.6) Word always fires up. It doesn't help it just means I need to close it down.

Could you please give me a hint as to how I can disable this irritating feature? Please note this doesn't happen when using Safari.


Thanks and regards
William