<edit>
Just noticed you said mod_rewrite.s instead of mod_rewrite.so - hope that's a typo in your question and not in the httpd.conf file! :)
</edit>
I'm more used to using Apache on Linux, but I had to do this the other day.
First off, take a look in your Apache install directory. (I'll be assuming you installed it to "C:\Program Files" here)
Take a look in the folder: "C:\Program Files\Apache Software Foundation\Apache2.2\modules" and make sure that there's a file called mod_rewrite.so in there. (It should be, it's provided as part of the default install.
Next, open up "C:\Program Files\Apache Software Foundation\Apache2.2\conf" and open httpd.conf. Make sure the line:
#LoadModule rewrite_module modules/mod_rewrite.so
is uncommented:
LoadModule rewrite_module modules/mod_rewrite.so
Also, if you want to enable the RewriteEngine by default, you might want to add something like
<IfModule mod_rewrite>
RewriteEngine On
</IfModule>
to the end of your httpd.conf file.
If not, make sure you specify
RewriteEngine On
somewhere in your .htaccess file.