Deployment Solution

we have a problem with our deployment, cause we are a school and sometimes the pc's are not beeing used for 2 weeks

so we need to make sure that when the pc starts it will get the task

if this possible

cause then we can't make sure that all the pc's have the software?

You can create a "Managed Software Delivery" policy, running "At computer startup" and add your tasks in there.
 

How do i do that

is it under manage-->policy?

Yep ...

At Software -> Managed Software Delivery

For this to work you will have to install the "Software Management Solution Plug-in" Agent

If it is a single task, you can also create a task scheduling policy (runs without any plug-in).

Don't schedule your task, but create a "Client Task Schedule" and select your task (thats a policy than will run your task ... f.e. "At computer startup").

This is done with right clicking any task folder (New -> Client Task Schedule)