I still have this iTunes bug, that iTunes creeps under the Windows taskbar. Can not acuratly reproduce it. But it happens with iTunes 18.104.22.168 on my home system with Windows XP SP2.
It does not happen everytime I start iTunes. I guess it only happens the first time after I startup the computer.
Let see when Apple will fix it.
By the way: I love iTunes, it is really cool.