HAL and bootvid

Hardware Abstraction Layer (HAL) insulates the OS from hardware by wrapping machine-specific details with an API that is implemented by HAL.DLL. Kernel mode device drivers invoke HAL routines rather than interface to hardware directly.

HAL implementation depends on hardware on which Windows runs on. HAL is located in system32 directory:

• hal.dll - standard PC 
• halacpi.dll - hardware with advanced configuration and power interface (ACPI) 
• halmacpi.dll - hardware uses multiple processors Sitting with HAL, 

bootvid.dll offers primitive VGA graphic support during boot phase. It can be controlled via the /noguiboot option in boot.ini.