To enable BigLBA on an XP computer, it is needed to change the parameter in the registry. Such an approach works well when the XP has been already installed, but if you need to make a fresh installation on the large disk, you can't change the parameter because the registry does not yet exist.
To work around this issue, you can do one of the following:
- Include the latest Service Park into the installation CD (this process is called "slipstreaming"), and then the full disk capacity will be available during install.
- Install the XP on a partition with the size, say, 100 GB, then install the latest Service Pack, enable BigLBA, and use a tool like Partition Magic to extend the partition onto the remaining space. Normally, we'd recommend that you backup before resizing a partition, but since this is a new install anyway, there is nothing useful to backup.