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
9. OSCDIMG.EXE -bETFSBOOT.COM -n -h C:\NEWPE C:\NEWPE.ISO
10. Burn the ISO image (not the ISO file itself) onto a CD-R.