I'm also getting an unhandled exception with the latest version. WMP11Slipstreamer v1.2.4.0 Detected source: Windows™ XP Professional SP3 Hotfixes: WindowsXP-KB941569-x86-ENU.EXE windowsmedia11-kb928788-x86-intl.exe windowsmedia11-kb929399-v2-x86-intl.exe windowsmedia11-kb929773-x86-intl.exe windowsmedia11-kb932390-x86-intl.exe windowsmedia11-kb933547-x86-intl.exe windowsmedia11-kb935551-x86-intl.exe windowsmedia11-kb935552-x86-intl.exe windowsmedia11-kb939209-x86-intl.exe WindowsMedia11-KB939683-x86-ENU.exe windowsmedia11-kb944110-x86-intl.exe windowsmedia11-kb944882-x86-intl.exe windowsmedia11-kb945381-x86-intl.exe windowsmedia11-kb946665-x86-intl.exe System.NotSupportedException: The given path's format is not supported. at System.Security.Util.StringExpressionSet.CanonicalizePath(String path, Boolean needFullPath) at System.Security.Util.StringExpressionSet.CreateListFromExpressions(String[] str, Boolean needFullPath) at System.Security.Permissions.FileIOPermission.AddPathList(FileIOPermissionAccess access, AccessControlActions control, String[] pathListOrig, Boolean checkForDuplicates, Boolean needFullPath, Boolean copyPathList) at System.Security.Permissions.FileIOPermission..ctor(FileIOPermissionAccess access, String[] pathList, Boolean checkForDuplicates, Boolean needFullPath) at System.IO.File.InternalCopy(String sourceFileName, String destFileName, Boolean overwrite) at WMP11Slipstreamer.Backend.CompressFiles() at WMP11Slipstreamer.Backend.SlipstreamWMP11() at WMP11Slipstreamer.MainForm.WorkerMethod(Object workerParam) Deleting "D:\OS\ROOT\i386\wmp11temp"... Done! The source being modified has not been damaged. All changes have been successfully reverted. Prior version 1.2.3.0 worked fine and nothing changed in my setup. Edit: I feel like such a fool for posting this. It now appears to be a problem induced by using the latest version of nLite. I had slipsteamed in some hotfixes prior to using WMP slipstreamer. I've done this in the past with no issue but not this time around. The slipstreamer works fine on a clean source. No idea why now it won't work that way now but at least it's working.