去掉URL中zentao无效

用的开源7.3版，想去掉URL中zentao，根据这个链接的指导无效，且出现白屏的问题。

http://www.zentao.net/book/zentaopmshelp/131.html

如果将D:\xampp\apache\conf中httpd.conf里面VirtualHost和ServerName的端口改成和前面第四行和第六行一样的端口号，就会出现白屏。

且VirtualHost 中的ServerAdmin和ServerName 修改成实际的内容无效，URL中还是有zentao.

# server basic settings.
ServerRoot "D:/xampp/apache"
DocumentRoot "D:/xampp/htdocs"
Listen 81
ServerAdmin zentao@localhost.net
ServerName localhost:81
PidFile "logs/httpd.pid"

………………

# If you want visit zentao like http://localhost/, uncomment these lines.
<VirtualHost *:81>
ServerAdmin cnagri-products@local.net
DocumentRoot "D:/xampp/zentao/www"
ServerName 192.168.22.28:81
<Directory />
AllowOverride all
Require all granted
</Directory>
ErrorLog "logs/error_log"
CustomLog "logs/access_log" combind
</VirtualHost>