Thanks for the suggestion but that didn't work. I have uninstalled the DVD player software (Power DVD), reset the default player in the DVD drives (suggested by Cyberlink support) unistalled the DVD drives one at a time, tried turning off all startup programs in msconfig (suggested on Plextor site. They report Blue Screen on inserting DVD when conflicting programs installed but in this case didn't help and besides problem occures with Plextor and Pioneer drives), upgraded all drivers and firmware for the drives, all to no avail. I even tried uninstalling the hard drive from Western Digital that had been reported to give the same error code but that didn't help. Logically it makes no sense that this is a driver conflict or software issue since the same drivers and software are installed whether I reboot with a DVD in a drive or not. I have floppy and CD set ahead of the HD as boot device in BIOS. Is the BIOS or windows sensing the presence of the DVD on startup and changing some setting that is preventing the IRQL not less or equal conflict? Something like that must be happening because once the computer has been booted with a DVD in one of the drives, it is like there never was a problem. Any more suggestions would be appreciated.