Pls Help Server2003 Disk drive full notice 1 meg free!!!

I recieved a notice today that my drive was full. HD properties free space 1mb of 40gig. I selected all folders on the drive and checked properties 4.7gig used. I am missing 35gig of
space. I checked recycle bin 200meg. Disk quota is off. show all files is on. Windows uninstal files = 800meg. I ran disk cleanup
it returned 25meg to the drive. Anyone have any ideas?