registry disapears?

When I type regedit in the run box, it will pop up then just disapear, I can’t access it at all, nor will my msconfig come up, (I can access that in SAFE mode) I have an eMachine 2.0ghz, 512meg DDR Ram, 40gig HD. I just can’t figure it out. Short of completely re formatting the hard drive what can I do?