I thank all of you for your valuable input. Since I use MS Words' 2000 version, this tip was particularly helpful. However, I could locate "password to open" in Save Options rather than General Options. Anyway, the problem stands solved.
Thanks for your co-operation.
Jack Doughty wrote:
In my version of word (Word 2000), go to Tools and General Options, which gives a space at the bottom for "password to open". Enter password, click OK, fill in same password to confirm it, click OK, save.
When you reopen the file, you now need to enter the password to open it.
[Edited at 2004-09-12 02:51]