It sounds like the CD you are trying is not bootable.
I don't think so, because he says...
If I disconnect the SATA-disk, I can boot from CD...
I ran into a problem here on one of the PCs at work which went along these lines:
- DVD drive was a SATA drive.
- BIOS has a setting for "SATA ROM: Enable/Disable"
- If SATA ROM: Enable, the hard disk is fast.
- If SATA ROM: Enable, DVD drive will not be bootable.
- If SATA ROM: Disable, the hard disk is very slow. I mean painfully, tear-your-hair-out slow.
- If SATA ROM: Disable, the DVD drive is bootable.
My only solution was to disable the SATA ROM for the amount of time it took to get the OS installed. After I got the OS installed, I changed the ROM to Enabled to speed up the hard disk.
Really poor design on the part of the motherboard mfr if you ask me...
Anyway, you say that your DVD drive is normal integrated IDE so that might not have any bearing on what you're doing.