If you follow the steps, you won’t have any problems.
Download Ultima Online Mondain’s Legacy full install client. You should not use any other UO install since some files may be corrupt or insupported by us. Install this and do not patch. Use one of the mirror below and please report bad links.
Download our files, and overwrite all files in your UO:ML installation (by default located in C:\Program Files (x86)\EA Games\Ultima Online Mondain’s Legacy)
You may now login (if you already applied for an account) So now,you can also download Razor or UOSteam. They are both supported and allowed, but do not ask help for it, we won’t help you with this.
If you ever need only the login, here it is: login.uoquartz.com,2593