VWFD.386 This VxD, when installed on a system running Windows in enhanced mode, allows DOS applications to determine if they are running in a window or full-screen. This is accomplished via the API that VWFD supplies TSTWF.ASM is a sample DOS program that uses the VWFD API. To install this VxD, copy it to your Windows SYSTEM directory and add the following line to your SYSTEM.INI. [386enh] ... ... device=VWFD.386