WHERE GET UPGRADE SOFTWARE - XP HOME TO PRO 64 Bit

[IPW]

Hello,
I am tired of Windows 7. I have my old XP Home Disc and am going back to that. Trouble is, I need to have 64 Bit capability so I guess I need the upgrade to Pro (SP2 or 3).
Any guidance on how to do this?
Thank you

 

[Emerald]

why do you need XP 64-bit?