Compaq prolinea 590 adding a tape backup

We have a 95 workstation with a cdrom. After adding the backup a seagate taravan 8gig the cdrom is not found. I used all the diffrent jumper settings on both, replaced the cable with a known good cable. Went to compaq to see if any rom paqs were there for this problem. Went to seagate to look at trouble shooting. I remove cable from backup cd works I use cable select.