Httpdocs write permission

[Abba bertina]

how can i set permission on files under the 'httpdocs' folder in file manager?
these files permission are inherited from httpdocs folder permission and i can't change httpdocs folder permission from File Manager.

i'm plesk administrator and i can change it from remote desktop but i'm searching for a solution for my domain customers.
this problems appears when my costumers try to install joomla and they need write permission for 'configuration.php-dist' file that places under httpdocs folder and they can't change its permission and when try to change from file manager the changes wouldn't set.

i found a similar bug in below url:
http://kb.odin.com/en/6640

Plesk Under Windows 2003 - IIS 6.0

 

[Abba bertina]

Parallels have to answer

i thinks this problem in very important and Parallels must answer or confirm that it is a bug