Use a working copy of RebootAion32.exe or similar or...
1.) (optionally) Save a copy of "Program Files (x86)\NCSOFT\AION_CLASSIC\bin64"
2.) Delete "Program Files (x86)\NCSOFT\AION_CLASSIC\bin64"
3.) Copy and paste "Program Files (x86)\NCSOFT\AION_CLASSIC\bin32" into "Program Files (x86)\NCSOFT\AION_CLASSIC"
4.) Rename "Program Files (x86)\NCSOFT\AION_CLASSIC\bin32 Copy" to "Program Files (x86)\NCSOFT\AION_CLASSIC\bin64"
You probably need to repeat this process every patch if you do it manually.