Bit confused how you are doing things. You boot off the Vista CD, the setup starts. You get to the part where it asks which partition to install on, then what do you do and what happens? Why won't it boot off the XP CD? Do you get to the message where it states "hit any key to boot from CD"?
He's got the same problem as me. I formatted my hard drive completely. (Installed it in another PC and did this). Put it back in my PC, then tried to install Vista. But it says BOOTMGR is missing. How do we get around this please? Thanks