logonui.exe and xp x64

[Sesshoumaru]

i was modifing logonui.exe for my win xp x64 when i noticed there is a syswow64 folder now, besides system32.

logonui.exe is in BOTH folders, with diferent size.

i was wondering, in the root of the x64 cd, there is an i386 folder, and an amd64 folder.

where should i put each logonui ? is it necesary to modify both ?