4D and 4D Server are Win32 application and can be run only under Windows 3.1(1) and Windows for Workgroups using a 32-bit thunking layer called Win32s. Frequently, your users will install an application which uses an older or proprietary version of Win32s. Often these versions of Win32s are incompatible with 4D, 4D Client and 4D Server. Many problems attributed with 4D and 4D server come from improperly installed Win32s or an overwritten Win32s thunking layer. Unfortunately, reinstalling 4D, 4D Client or 4D Server will not always solve the problem, particularly if the other application has modified the Windows system files. Thus, it is sometimes necessary to remove Win32s manually. This document will describe how to properly remove the Win32s thunking layer in preparation for a fresh install of Win32s.