i got 2 hard disks. in one of them i got vista installed. and in the other i try to install XP, and it works, the only problem is vista doesnt work after that. it always loads xp, and if i select the vista HD as the only boot-ing hard disk, it says some file is missing and dont boot, whereas i never touched that HD, during or after installing XP. Could someone tell me what possibly went wrong, and how i can install WIN7 on the second harddisk without messing vista up
You should always install the oldest OS first. Installing XP after Vista has deleted the Vista bootloader, so you now need to boot with the Vista dvd and run Vista repair to fix the bootloader.
Once that is corrected, when you get the Windows 7 upgrade, run it from Vista to upgrade Vista and retain XP and your Vista programs and settings.
It's advisable to make a backup of your important files in case of problems.