How to create tasks to registered users

[seregarem]

I create a corporative site. I need, that a chief can create tasks to his employees: a chief creates a new task (write a text, attach files and etc.) to each employee, then an employee logs in and in his message center reads the new task. After execution of this task, marks it like "completed" or "uncompleted". So, what modules should I use to make this?

[Rolf]

Perhaps http://dev.cmsmadesimple.org/projects/servicedesk ...

[seregarem]

It's good to me, but how to attach a file to a message in this module?
Also, I can't open a detailpage - it just writes:

Unknown value for parameter display used. Please notify webmaster.