This is a Mac G4, 867 MHz, Quicksilver, OS 9.2.1, used strictly for ProTools. Have had two Adaptec SCSI cards (2906 and 2930CU) installed for quite awhile to drive two Glyph hard drives and a Yamaha 2100 CD recorder. Also have five firewire hard drives installed. I just installed an Adaptec 39160 SCSI card to drive several Glyph drives with Seagate 10,000 rpm drives. 39160 and installed drives show normally in SCSI Probe. I didn't run the Adaptec CD-ROM for the 39160 because of the subject problem. The internal drive (Pioneer CD/DVD 103) shows up in Toast Titanium, although I haven't tried to record anything. I have been going through the Mac troubleshooting procedures, but I must be overlooking something. Right now even the Mac OS 9.2.1 Base Extensions list will not bring up the drive to the desktop. Is there anything I can do short of removing the 39160 board and hoping for a return to the previous state of operation? Thanks in advance for your suggestions. And thanks for this great service which I just discovered.