1) Put the HDD in another computer.
2) Use a Windows 98-floppy, to create a FAT32-partition on the HDD.
3) Format the partition and make it bootable (format c: /s)
4) Copy Windows XP's installation directory (i386) to the HDD.
5) Put the drive back into the laptop, and boot from the drive.
6) CD to the i386-directory, and start the installation by typing WINNT.