It seems that this has more to do with your directory structure. when you put the slash in front, the path will be absolute to your webroot directory (the same directory where http://domain.com points to). so you have to bring the ms_temp folder there.
that is exactly that I do, I put the ms_temp in the webroot [htdocs] and remap the Apache Alias /ms_tmp/ "C:/ms4w/Apache/htdocs/ms_temp/" and shazan! run!
but i would like that apache alias Alias /ms_tmp/ “C:/ms4w/Apache/htdocs/YiiProject/ms_temp/” for the ms_temp stay within the scope project, but this don’t run