Excel.exe/Word.exe Error

I’m use Windows 2000 Prof, and i have problem when everytime we finished using word/excel, i find this error : “Excel.exe has generated errors and will be closed by windows …” or “Word.exe has generated errors and will be closed by windows …”.
I try to find the problem, and the problem is when i opened the attachements (word/excel) in Microsoft Outlook (outlook Express), that errors messages will pop-up. And if i’m not opened the attachements that error will not pop-up.

So, How to fixedthis errors ???