I can't recall if you can do it directly at the server itself or not (wouldn't hurt to try).
But, yes, login as Admin, go to Dos in Windows (Start>Run, type 'command' and hit [Enter]). Then go to the drive that's mapped to your sys: vol and type 'purge /A'
You can see where a drive is mapped by simply going to My Computer and looking at the drive descriptions. If you don't have a drive mapped to the root of sys, you'll need to map one. You can do so in Network Neighborhood by going to that Server and right clicking the sys: vol, choose Map Network Drive.
If you have multiple volumes, you'll need to purge on that one too.
Oh, and it shouldn't be a prob with others logged on.