Windows 7: Run scheduled tasks in background

Hi

I created a task for my backup/file sync. It's a simple task that runs a batch file on each 5 min for 9 hours. The real problem is, a command prompt appear on every run because of batch file. And I'm trying hide this annoying behaviour.

I did this before in my xp machine with running task as "NT AUTHORITY\SYSTEM" in schedule tasks, so it runs in background.

I read some suggestions in forums, like making a shortcut of that batch file and setting that shortcut to run as minimized window or using *vbs scripts or using cmdow window hider...
Actually cmdow works not that bad, but still each run a command prompt flashes...

So, is there any way to make that task, is a background process..