I am trying to backup Windows 7 to an external drive. I keep getting an I/O device error. I've used CHKDSK on both drives but still get the same error. Can you help please? Dave

This can happen if your virus scanner (or another heavy disk activity application) is accessing the drive. You could try running chkdsk in safe mode: http://windows.microsoft.com/en-US/windows7/Start-your-computer-in-safe-mode If you run chkdsk in safe mode and you're still having trouble backing up, try preforming a clean boot to disable any third party applications and then test backing up: http://support.microsoft.com/kb/929135Please 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.