How can I backup C:\Users?

I'm upgrading my PC and the only important thing on it is the C:\Users directory. I would like to do a backup of it to another directory, but attempts to do so with robocopy failed.

I was trying (in a Run As Admin CMD.EXE):

robocopy C:\Users D:\backup /mir /mt /log:log.txt /eta /tee /zb

Also with /sec added. Both give:

2013/08/19 21:01:24 ERROR 1921 (0x00000781) Scanning Source Directory c:\Users\A
ll Users\Application Data\Application Data\Application Data\Application Data\App
lication Data\Application Data\Application Data\Application Data\Application Dat
a\Application Data\Application Data\Application Data\Application Data\Applicatio
n Data\Application Data\Application Data\Application Data\Application Data\Appli
cation Data\Application Data\Application Data\Application Data\Application Data\
Application Data\Application Data\Application Data\Application Data\Application
Data\Application Data\Application Data\Application Data\
The name of the file cannot be resolved by the system.
Waiting 30 seconds...

Oddly, there is no C:\Users\All Users directory. But I take it that robocopy can't backup C:\Users.

So how can I make a copy of it?

Just drag and drop copy with Explorer. You won't get the files being used by the system. ntuser for example, but will get everything else. Skip what won't copy.
If you want it all, you're best off taking an image. Much simpler than mucking with system files.
Check again for "All Users." I always have that, but it might be particular to my install/configuration.