let me guess VISTA yung preinstalled? ganun talaga ang mga vista na installed by PC manufacturers meaning the desktops was bought as a packaged deal like DELL or HP, obviously yung may ari nyan nagupgrade kaya nagdispose ng 400gb(not an easily available size) and may have tried to do what your trying to do and HINDI gumana kaya binenta na lang
manufacturer installed VISTA will not allow a separate install of another OS or even access a drive you wish to install an OS specially XP
nangyari ganyan sa Toshiba laptop ng uncle ko lahat ginawa namin to try and install