tyrram

alright this is complicated but here goes. i managed to install a dual boot XP x64 and vista ultimate x64 when i started up before i got and option screen to choose which installation i wanted to boot to either the vista which was the default or an older version of windows which was the XP x64. well the XP x64 didnt work out too well it must have been a bad install so i wiped thet partition and reinstalled XP x64 which made XP x64 the default drive the system would only boot into XP x64 and i no longer had the option to choose. I figured this was because XP x64 was now on drive c and vista was on drive H. So i booted from the vista cd and managed to repair the boot so i could now get into vista again but i still do not get the option to choose it boot directly into vista x64. SO....question is, how do i restore the option menu to choose either one or the other vista x64 or older windows version (XP x64) ?? XP x64 is just sitting there perfectly fine waiting for me to be able to boot into it. pls help !