Well, first I would recommend using wamp for php on windows, and then I would recommend using the fileinfo extension instead of mime_content_type():
http://www.en.wampserver.com/
http://pecl.php.net/package/fileinfo
http://www.php.net/manual/en/function.finfo-file.php
Wamp makes dealing with extensions quite a bit easier, among other things.
However, if you want to stick with IIS and mime_content_type(), then I'll need a few more details. Are you saying that you have your magic.mime file in c:\php and phpinfo() says it's looking for it in c:\php5, or are you saying that you don't have that file at all?
If you do have it and it's just looking in the wrong place, then you can fix this by opening your php.ini file and setting "mime_magic.magicfile" to the right directory. Also, according to
this guy, IIS needs the line "mime_magic.debug = Off" in your php.ini as well.
If php wasn't configured with that extension at all, then you'll need to install it. Instructions for that can be found here:
http://www.php.net/manual/en/mime-magic.installation.php
