Makes classic Ultima Online clients portable by intercepting registry queries and returning paths derived from the client's own location on disk.

All classic UO clients read their installation path from the Windows registry:

HKLM\SOFTWARE\Origin Worlds Online\Ultima Online\1.0
    ExePath    = C:\Program Files\Ultima Online\client.exe
    InstCDPath = D:\

Without these keys the client shows "Ultima Online does not appear to be installed correctly" and refuses to start. This makes it impossible to relocate, duplicate, or run multiple client installations without editing the registry each time.

Place dsound.dll in the same directory as client.exe. The proxy intercepts UO registry queries and returns paths based on the client executable's actual location (via GetModuleFileNameA). Each client directory becomes fully self-contained - no registry keys needed.

Since advapi32.dll is a Windows Known DLL (always loaded from System32), it cannot be proxied directly. Instead, dsound.dll (which is not a Known DLL and is imported by every classic UO client) acts as the entry point: the loader picks up the local copy, which patches the client's import table at runtime to intercept the advapi32 registry functions. All DirectSound calls are forwarded to the real system DLL.

Place dsound.dll in the same directory as client.exe.

Place dsound.dll next to client.exe and tell Wine to load the native version:

WINEDLLOVERRIDES="dsound=n" wine client.exe

Or set the override permanently for a prefix:

wine reg add 'HKCU\Software\Wine\DllOverrides' /v dsound /d native /f

Requires MinGW cross-compiler:

make

Produces dsound.dll.

If you prefer the traditional approach, you can download and import the uo.reg registry key. Edit the paths inside to match your installation directory, then double-click the file or run:

regedit uo.reg