Manage to install,but can’t use WP

I manage to install WP2.0 on my host,but when I just finish installing and jump to the Login page and press the “login” button,instead enter the site management,I download the “wp-login.php” and then I can’t enter WP,
It’s a strange question ,do anyone knows the answer?
My PHP version is 4.4 and MYSQL works well.
THANKS!!!