If you have a dual boot of Home and X64 in that order the boot.ini file
will be on the Home partition. To see it you will
   have to open WinExplorer>select Tools>Folder Options>View>Check Show
Hidden Files and Folders and uncheck
   Hide protected operating system files. Open the Boot.ini file and where
it says Timeout=30  change that to 2. You can
    also highlight the line
  multi(0)disk(0)rdisk(0)partition(0)\WINDOWS="Microsoft Windows XP64 " and
delete it. It may be a little different
  but as long as it has the XP64 Identifier  you can delete it. Save the
changes and format the XP64 partition.
   You can do that from XP Home MyComputer>rt click on the 64 partition and
choose format.