The I999xxxx error means that the PS/2 (or INDUSTRIAL) computer can't find system programs from the REFERENCE disk on the first 1mg of the Hard Disk.
The error code might vary slightly (I9990020 I9990030 etc.), depending on the capacity of the SCSI HD.
The Model 95 (and also perhaps the Model 90 - anything 8595 or 9595) actually performs a mainframe style IML on load up. I've also seen this error in the IBM 7546 INDUSTRIAL computer.
The fix is to copy the programs from the REFERENCE disk (there is a pick called RESTORE SYSTEM PROGRAMS), which creates this protected first Mg section. You may also need the DIAGNOSTIC disk for your particular model. Get these files from the PS2 or INDUSTRIAL computer Web Sites.
It's been reported that the RESTORE SYSTEM PROGRAMS will also delete all info from the drive, since it blows away any existing operating system from those sectors. This did not happen when I encountered this problem! But do be aware, as always with any hard drive utility, that all information could be lost!
For more information see I999 IML ERRORS (Model 90 & 95)