I'm not sure that you will get the ost copy to work too simply...

the ost is an open file and will be locked - to copy this you will need to have VSS (shadow copy) working to image the partition and copy from the partition - vista has VSS installed - so its just a matter of getting the command line queries going - should be able to find these in a Google search (I can assist if you like). If you are using XP - you will need to download the VSHADOW SDK and use that - again run from command line...

Alternatively - what I do - is install Synctoy 2.0 (beta) and set up a contrib. sync to the end location for backup. For this to work though, I close outlook down each night...

I hope this gets you started on the ost copy/backup...