I don't really quite understand what you are asking.

Are you talking about trying to get your old LogonXP skins to work with the new LogonStudio for XP/Vista/Win7?  If so, the answer is you can't really.  Other than to pull the 100.bmp image out, rename it, put it in the appropriate folder, and use it as a background.  All the other skinning on the screen (user name sections, etc) isn't done in the new version, it just loads the main background image.

If you are on XP, you can have both the old version and new version installed on the machine, they are separate programs.  If you switch back and forth between the two, I suggest applying the Windows default on the version you have been using each time before you apply a logon with the other version, I don't know what might happen of you don't.