PC Start With Slave OS, instead with the primary, why?

[Van_Richten]

I have an old HDD that I want to use it in
other computer, when I install the HDD on my pc as slave,
I also change the jumper to slave. So when the computer
start, It detect the Os of the slave drive instead the
primary drive, why is that. The Bios is also set to
start with the first drive, in this case the primary.
In the post Everything is ok, The primary is detected as such and the slave too.

Any Help please, thanks.

[ajzchips]

The primary partition of your master HDD might not have been activated, so it skips to your slave HDD.

[Van_Richten]

Ofcourse the primary partion is activated, that is the first thing that you do. When you format a HDD you also make a Primary partition. Both have a primary partition.

[Denniss]

Double-check the Master/Slave jumpers on both drives
If using an 80wire UDMa cable make sure you connect master to the black end and the slave drive in the grey port in the middle

[edwin]

Ofcourse the primary partion is activated, that is the first thing that you do. When you format a HDD you also make a Primary partition. Both have a primary partition.

fdisk, option 2 and check. Not ofcourse, only if you answer yes on all questions when partitioning the disk, if you do something manually, you have to ACTIVATE the partition on that disk.

[KachiWachi]

Depends what he really wants to do.

He could delete all partitions on the new Slave, then set it up as an Extended Partition Drive only (to preserve drive order).

He doesn't mention drive sizes or OS involved...