Judging by the look of the case's condition (a pic of the front would have helped more) the power switch is still in tact, it just doesn't have the front panel button. There should have been a SMALL black switch in a hole in the front between the drive and the grill, to the right of the usb ports.
That case was basically used from Pentium 4 and up. It's an SFF case. I used to repair a LOT of these.
The front panel jumpers are marked on the attached image. I believe the power jumpers are the first two on the right if it's at the top of the mobo.
I know my reply may be too late, but if everything worked they were a half decent system.