Customizing the URLs of WordPress Login and Sign-up Pages?

I have Multisite installed. I have whitelabeled it using the Whitelabel-CMS plugin, but I can’t customize the URLs of the sign-up and login pages.

Can I change the URL of my multisite’s login page? I want to change the URLs of sign-up, login, and registration pages .

Sign-up: http://domain.com/wp-signup.php
Login: http://domain.com/wp-login.php/
Registration: http://domain.com/wp-register.php/

Could you help me with the customization of these URLs? Is there such possibility?

Update:
I have changed the .htaccess file like this :

<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteRule ^login$ /wp-login.php [L]
RewriteRule ^signup$ /wp-signup.php [L]
RewriteRule ^register$ /wp-register.php [L]
RewriteRule ^index\.php$ - [L]

# uploaded files
RewriteRule ^files/(.+) wp-includes/ms-files.php?file=$1 [L]

RewriteCond %{REQUEST_FILENAME} -f [OR]
RewriteCond %{REQUEST_FILENAME} -d
RewriteRule ^ - [L]
RewriteRule . index.php [L]
</IfModule>

I am not sure what to do next .

Solutions Collecting From Web of "Customizing the URLs of WordPress Login and Sign-up Pages?"

You can use a htaccess file to rename the login and registration addresses to easier to remember versions:

http://wpguy.com/articles/an-easy-to-remember-login-address/

Using what was in that link we can further extend the simple login address into a simple signup and a simple register address as follows:

RewriteRule ^login$ /wp-login.php [L]
RewriteRule ^signup$ /wp-signup.php [L]
RewriteRule ^register$ /wp-register.php [L]

Remember these need to go directly after the RewriteBase / statement