BOOTMGR is missing Press Ctrl+Alt+Del

Question

BOOTMGR is missing
Press Ctrl+Alt+Del to restart.
Im trying to format an older computer with XP Pro. I physically took out the only hard drive in the computer and hooked it up externally to my laptop to save files and burned copies of the data my friend needed. I then formatted the drive (my laptop's OS is Vista Home Premium), and reinstalled the hard drive (an old 40 gig Maxtor drive) into it's old computer. The motherboard is an MSI KM4M-L. I changed the BIOS to boot from CD drive, and each time the message:
BOOTMGR is missing
Press Ctrl+Alt+Del to restart.
What can I do to solve this? What do I need to change? I have the XP pro disc and my product key.