Well at the first place, if you are using microsoft iis server, it should probably be for asp files probably! but if you are
How ever, in any case if you still need to use the microsoft iis server for your files, and also need to use the .htaccess, there is no such alternative for iis server by default as far as i know! you have to install this module for iis server called mod_rewrite for iis server. This will enable the mod_rewrite facility for your microsoft iis based server running php files and you will be able to use the .htaccess easly. You can download the files from the following link along with all details and installation instructions:
http://www.iis.net/downloads/default.aspx?tabid=34&g=6&i=1470