You can't route web address to any folder on windows, http is a web protocol and must have a web server listening on other end. What you can do is to set up virtual host in Apache, preferably a subdomain, and make folder you want to be accessible from the web a DocumentRoot of that host. So:
In host file set
127.0.0.1 myfolder.localhost
and add these lines to httpd.conf, Apache configuration file (or extra/httpd-vhosts.conf, make sure it's being included by main httpd.conf)
NameVirtualHost 127.0.0.1
<VirtualHost 127.0.0.1>
DocumentRoot "C:/webroot"
ServerName localhost
<Directory "C:/webroot">
Options Indexes FollowSymLinks MultiViews +Includes
AllowOverride All
Order allow,deny
allow from all
</Directory>
</VirtualHost>
<VirtualHost 127.0.0.1>
DocumentRoot "D:/myfolder"
ServerName myfolder.localhost
ErrorLog "D:/myfolder/logs/error.log" # if you want separate logs for this folder
CustomLog "D:/myfolder/logs/access.log" combined
<Directory "D:/myfolder">
Options Indexes FollowSymLinks MultiViews +Includes
AllowOverride All
Order allow,deny
allow from all
</Directory>
</VirtualHost>
You must also setup regular webroot for localhost as shown above, otherwise it won't be accessible anymore.
Another (simpler) option to access different folder would be to create in your webroot a hard-like-link to other folder using junction program from Microsoft.