Windows 98 was the first operating system to use the Windows Driver Model (WDM). This fact was not well publicized when Windows 98 was released, and most hardware producers continued to develop drivers for the older VxD driver standard, which Windows 98 supported for compatibility's sake. The WDM standard only achieved widespread adoption years later, mostly through Windows 2000 and Windows XP, as they were not compatible with the older VxD standard. With the Windows Driver Model, developers could write drivers that were compatible with other versions of Windows. Device driver access in WDM is actually implemented through a VxD device driver, NTKERN.VXD, which implements several Windows NT-specific kernel support functions.