Here's where your client executable files will end up:
UO 2d ("Classic Client") that can only access production shards
C:\Program Files\EA Games\Ultima Online The Eighth Age (or something comparable)
Kingdom Reborn client that can only access production shards
C:\Program Files\EA Games\Ultima Online Kingdom Reborn
UO 2d ("Classic Client") that can only access Retribution test shard
C:\Program Files\Electronic Arts\Ultima Online Stygian Abyss Classic
UO SA ("Enhanced Client") that can access ALL shards
C:\Program Files\Electronic Arts\Ultima Online Stygian Abyss
Desktop icons will be labelled as follows:
UO 2d ("Classic Client") that can only access production shards
Ultima Online The Eighth Age (or something comparable)
Kingdom Reborn client that can only access production shards
Ultima Online Kingdom Reborn
UO 2d ("Classic Client") that can only access Retribution test shard
Ultima Online Stygian Abyss Classic
UO SA ("Enhanced Client") that can access ALL shards
Ultima Online Stygian Abyss
I thought I'd throw in some instructions here too if you want to have UO Assist run with the UO SA Classic client. When you start up UO Assist, click on the Settings button on the bottom right corner of the UO Assist patch screen.
Then in the center of the Settings gump you'll see next, click the radio button next to the "User defined" line and type the following into the box:
C:\Program Files\Electronic Arts\Ultima Online Stygian Abyss Classic\client.exe
When you log on this way, you will get the usual UO Assist warning about the client has patched, blah blah blah. UO Automap will work for you too if you can get UO Assist running. However, it will not provide any maps for the brand-new areas, including anything that's changed in Fel, Tram, Ilshenar, or Malas in conjunction with the expansion.
BIG CAUTION: I believe that having the UO SA Classic client start with that executable file (rather than UO.exe in the same folder) will bypass the patching process. Therefore it is very important that you periodically log onto Retribution with the classic client WITHOUT first starting UO Assist so the client receives all patches. Also, be forewarned and don't expect much support if you try to set up UOAssist to recognize new items as resources (e.g., new potions, etc.). If there's new stuff in that client, I'm pretty sure Tugsoft has not updated it to recognize them.
If you made the above adjustment in the UO Assist Settings gump, you will need to change back to the "2d client (client.exe)" option above the "user defined" option when you want to play a regular production shard.