summerz on "404 error at wp-signup.php (on Windows)"

i setup multisite using define('WP_ALLOW_MULTISITE', true);

i choose multisite as woking sub-domains and everything looks okay like making new blogs, installing plugins, registering themes... except /wp-signup.php.

i try to call /wp-signup.php and it gets to 404 error.

it is okay with /wp-login.php and /wp-admin/ though.

i install wordpress with Web Platform Installer on Windows Server 2008.

Anyone to know how to fix this?

thanks in advance.