need help re BIOS settings so cmptr will recognize the d drive...

a while back i and an online 'tech' tried to install xp pro on my dell gx1. after determining the local (c) drive was too small. i got back to 98 SE which was installed on the system. now the cmptr wont recognize the cd rom. it does not appear in 'my computer', just the diskette and local drive. no d drive icon. In device manager, cd rom controllers are there next to a MINUS not plus sign and but there is a yellow exclamation point over 'sony proprietary CD rom controller' I think what my problem is is that the BIOS setting are at issue and not recognizing/acknowledging the cd rom drive. this 'tech' had me changing BIOS settin and i think the CD drive was turned off there...anyone know where i go in BIOS to reset settings??? BIOS AO7, 98SE...