Sharing violation in MS Word files

My OS is Win98 and I’m using MS Word 97.
The problem is when I work on word files some times it leaves the temp file and when I open the document next time it shows an error saying this file is used by the user, if I find and delete the temp file (~.tmp)then the file works fine and it repeats again later. Why this temp files are not getting deleted ? How can I fix the problem by setting up to delete the temp files as I colse the file ?

Thnks