Although the installer for the DOS Compatibility Card software v1.0.7 is included on the CD, this software is not supported for use with System 7.5.3.
DOS Compatibility Software Update 1.5 is now available from the online services. Apple recommends using this version with Apple DOS Compatibility cards, except for those used in Macintosh Quadra and Centris 610 computers.
This article can help you locate the software update mentioned here: