Couple weeks ago, I updated OS from V25.1 to V27 with MKIV successfully. I got the same problem as JV which the CD version 25.1 stucking in the NAV and screeen was black while trying to downgrade from V27 to V25.1 before upgrade back up with V27 flashing logo. This CD with V25.1 was used to update my NAV OS previously. Need help!

1. How do I eject the CD?
2. Should I use the V27 CD to update NAV OS again?
3 Will my NAV OS wiped out?

Thanks,