This problem has other threads in other forums related to specific networking or other MS products. This is a more generic problem that is reproducible. On a Dell Quad Core machine with 8GB memory, Win 7 Ultimate 64 bit, I am unable to copy large files (over 64GB in size) from one directory on the same drive to another, or from one drive to another - no network involved. Copies fail with the Error 0x80070079: The semaphore timeout period has expired. I have tried this with Safe Mode, and Clean boot, both with and without the MS Security Essential active, and the problem repeats. THIS IS A REAL PROBLEM FOR SOMEONE DEALING IN LARGE FILES, AND BREAKING THEM UP, COPYING, AND RE-ASSEMBLING IS NOT AN ACCEPTABLE WORK AROUND.

Hm, doesn't seem to be a problem on all systems. I just copied a 67 gigabyte file from one folder to another on the same hard drive and between drives, and I was not presented with the error you have described. Mine happens to be a Dell dual quad core machine running Windows 7 ultimate x64. The single drive copy took a while, as expected - about 20 minutes or so, while the drive to drive copy was much faster (10 minutes). Did you get the error after a significant amount of time had elapsed? Have you looked in the event logs? It's possible you're taking an error from the drives themselves. -Noel

Hi, I suggest updating BIOS and hard drive driver from manufacture's site, then checking the disks. Open an elevated CMD and type the following command: chkdsk [Drive letter] /f /r Or you can use robocopy instead. More information for reference. http://technet.microsoft.com/en-us/magazine/ee851678.aspx Best Regards, Niki Please remember to click "Mark as Answer" on the post that helps you, and to click "Unmark as Answer" if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread.