I copied some Visual Studio C# build output files from a share and experienced copy errors with some of the files. copy \\computer_name\share_name . /s 1,422 files copied 101 failed The files with the error had a prefix added to the path resulting in the error. \\?\\\computer_name\share_name\dir1\filename.ext => D:\dest_folder\build_num\dir1\filename.ext TCC: (Sys) The filename, directory name, or volume label syntax is incorrect. Here is the distribution of C# build output file types that had that problem: exe: 4 pdb: 17 dll: 74 config: 6 Here are the totals for the files on that share: Total for: \\computer_name\share_name\* 669,800,184 bytes in 1,523 files and 1,124 dirs 672,845,824 bytes allocated This error was experienced in TCMD and TCC/LE. TCC 13.03.47 Windows 7 [Version 6.1.7600] TCC Build 47 Windows 7 Build 7600 TCC LE 13.03.45 Windows 2003 [Version 5.2.3790] TCC LE Build 45 Windows 2003 Build 3790 Service Pack 2 When I copied from the share using Windows Explorer, there were no errors.