external SCSI CD-ROM drive problems

Hi!
I would like to install WIN95 on a 6100 with a 486 card. I´m using "PC Compatibility 1.6.4" with the DOS CD-ROM driver "CDROM.SYS".
The problem is that everything is fine - I edited the "AUTOEXEC.BAT" and the "CONFIG.SYS" like they should be - but the sytem denies access on "E:" - which is the CD-ROM drive - and gives the following message: "CDR103: CDROM not High Sierra or ISO-9660 format while reading from drive E:". In fact I did put an original WIN95-CD into the drive. The CD works fine in another PC.
I guess the Apple "CDROM.SYS" is not the right driver for me i.e. for an external SCSI CD-drive.
I´ve checked "scsiboot.exe" which doesn´t work.
Anyone an idea?
Thanks a lot...