before making any suggestions or (false) assumptions - did you reinstall the base OS or did you "just" swap the hardware and kept all software and config?
In this case you might need to adjust some settings, especially in hpfs386.ini to optimize memory usage...
BTW: DId you change mainboard/cpu only or anything else (e.g. SCSI adapters).
Are you using (onboard) IDE drives or SCSI?