You have to make the 64-bit WinPE CD yourself.

  1. Copy the \WinPE folder from the OPKTools CD to your hdd (e.g. c:\WinPE)
  2. Open a command prompt
  3. C:\
  4. CD\WinPE
  5. Insert the x64 version of XP Pro (cancel the autorun)
  6. MKIMG D: C:\NEWPE (Where D: is your CD-ROM drive letter)
  7. Make any modifications to the C:\NEWPE folder you might need (add network drivers, mass-storage drivers, etc. )
  8. CD\WinPE
  10. Burn the ISO image (not the ISO file itself) onto a CD-R.