Yes, you can change it by editing Plesk file



%plesk_dir%\admin\plib\locale\messages_en.php3



replace paramater with your own

‘login_up__login_label’ =>



For example:



‘login_up__login_label’ => “Log in to Plesk 7.5 for Windows”

can be changed to

‘login_up__login_label’ => “Welcome to my host”



Note:

If you use another language not English then you should edit an appropriate file messages_**.php3

For example if you use French you should edit messages_fr.php3

German => messages_de.php3