The error message tells me that Windows Backup skipped backing up system image because one of the critical volumes does not have enough free space. Free up some unnecessary files and try again.

Formatting the external hard drive, and clean up the C drive to free space made no difference.

I choose to back the C drive which contains system files only and after about 50%, somewhere in the Office files it crashes. my C drive contains only 43.5 GB while the hard drive has over 300 GB.

have checked it for bad sectors and tried with a 500 GB external hard drive but it made no difference.

If I'll use the standard copy function to back up program and system files to the external drive, will not create a drive image and if it wont work like an image.

If something goes wrong in my hard drive due to a virus or a software clash I wont be able to use it.

I have run into problems with the file name and\or path being to long, causing a failure.

When that happens I usually get a message specifically saying that. Since this is an imaging process, you may get a different message..,

Since you have isolated this to Office files, see if you can actually copy some of them to the external drive normally...Program Files for example

I understand that...I was just suggesting a test of your Office Program Files...to see if they would do a simple copy and paste without generating an error...or some of your saved Office files.

This wouldn't solve the problem, but would at least identify it.

When I've had these errors, I had to copy to or from a higher up directory to get past the problem.

For example...I might have to save or copy a file to C:\Documents or C:\ Office, instead of C:\Documents\Office