Scsi disc on existing PC with OS Win XP

I got a PC with win xp x64.Now i have SCSI disk and i want to have Win XP on this Scsi disk.
I instaled OS on SCSI disk and when i turn on the pc it askedt me wich operating system i want to run,i choose win xp on scsi disk and i get error mesage that ntoskrnl.exe is missing.Ive seen similar post on this forum about this problem,and i think that the problem is becouse scsi disk is not C: but old disk is.
Now im thinking that i unpluged old disk and leave just a SCSI disk and reinstal XP it would probbably be C:,but the problem can apere when i plug in an old disk wich will be the same C:,and here can be a problem.
Ok,if an old disk can be pluged in,when win xp on scsi works,than i just rename volume label/drive,but the disk can not be pluged in when system is on.

Can somebody tells me for 1st,how can i set that the scsi disk is master,becouse i have adaptec controler for it,disk have a jumper select but this is not the same jumper select as in non SCSI disk.
This is the second problem wich i must know,before i solve the problem of booting.
Ill try to disconect disk and leave scsi on,install xp and see how its work,but for the first i must know this abut scsi dosk,how its mastered and so on.

Mamybe i must do some configuration on start up,becosue pc see the SCSI drive and i get second setup to configure a lot of function but i diont know how if necessery becouse its my first time with SCSI disk

I got 68 pin model.

When you have only the SCSI disk, install Windows XP. Now shutdown and connect the old disk. On booting it will see two OS installed there but the old disk wont be C:. Restart with the 1st OS option(that on the SCSI disk). If you have have data on that disk make a partition with Partition Magic on the old disk and shift all your necessary documentations and other data to the non-boot partition. Now format the boot-partition.
Then put your Windows XP installation cd and boot from that and bring up the recovery console.
Now type the command "fixmbr" and hit enter.
Exit, take out the cd and restart from harddisk.
Now you have only one OS installed at SCSI drive while the old disk hooked in.
If still unable to boot, don't worry.
Insert your XP cd again and boot from that to bring recovery console.
Now type the following and hit enter after each line,

Attrib -H -R -S C:\Boot.ini (press enter)
DEL C:\Boot.ini (press enter)
BootCfg /Rebuild (enter)
Fixboot (enter)
Exit (enter)

then take out the cd and boot normally.

This is one of the various ways you can solve your problem.