HFSLIP is an open source utility designed to update a Windows 2000, XP or 2003 installation source with the latest hotfixes. The binaries of fully supported hotfixes are slipstreamed directly. This means that original files are being replaced with the newer versions present in the hotfix executables you can obtain from the Microsoft Download Center. In the rare occasion that a hotfix isn't supported, it is integrated instead. It leaves these uncommon hotfixes or updates as they are and places them in the SVCPACK folder, to be installed automatically near the end of Windows setup.