I have installed win 8 on one drive and windows xp on the other. In the setup it says to boot on the win8 hard drive but it only boots on xp. I can get to the win 8 hard drive. but it is not booted. It sees it at start up and in the bios setup.
In the computer disk manager it says the xp drive is boot and win8 is system.
How do I make them dual boot?
It would appear that you have installed Windows XP after Windows 8, thus replacing the Windows 8 boot files with those of Windows XP which are not compatible with newer versions of Windows. It is fairly easy to recreate the BCD using bcdedit.exe and bootrec.exe as outlined in the instructions for rebuilding the BCD which can be found here.
You may also want to re-enable the ability to use the Windows 8 graphic boot menu, which you can do by disabling Emergency Management Services with the following command: