How to recover password on a xlsm file, which changed automatically from an xls file

I have a simple file with only one simple macro.... i noticed that the file, for some reason, had been changed to .xlsm from simply being .xls
It remained open on my laptop for sometime and then i decided to close it... the file was protected with a password to open.
Since then i have not been able to open this file... and i am quite sure that i am typing the right password.
Can anybody help.

OK ... can anybody just help me convert my file back .xls format from .xlsm.... maybe then my password would work?