Static virtual devices can open and retrieve values from the registry during real-mode initialization. During this time, the registry is read-only and only the keys and values under the HKEY_LOCAL_MACHINE key are accessible. Virtual devices call these functions by filling registers and calling the loader services function or by using one of these real-mode registry function macros:
LDR_RegCloseKey
LDR_RegEnumKey
LDR_RegEnumValue
LDR_RegOpenKey
LDR_RegQueryValue
LDR_RegQueryValueEx