Vista(x64) - XP.Pro.SP2(x86) Dual Boot Install Issues

Hi there!
Very good tutorial indeed. Nonetheless, I was not able to fully install XP Pro SP2 secondly to a Vista Ultimate x64 machine. I used a perfect original XP CD that began installation by partitioning and formatting the HD (in which I have installed the Vista x64) an then installed the XP files like a dream. However, when it reboots, the computer halts by the message "press any key to install from CD/DVD". Some funny colored ASCI characters also appears on screen (somewhat like a virus, though none was detected thru my previous scanning with both NOD32 and Norton). Any guess (and/or troubleshooting)? Thanks anyway.