Overkill command crashing because undo file over 2,000,000?

I am using autocad 2011.

I am trying to get rid of the duplicated line from a 30M file.(too much lines duplicated)

When I using OVERKILL command on more than 1000 objects, autocad crashed.

the error pop up is “fatal error: cannot write to undo file (probably disk full)”

Solution I try: I delete almost all files in temp folder, and it raise to 2000-3000 files, but still very frustrating..

And this undo.ac$ file may be the one causing problem.

As long as it reach close to this number 2,000,000kb, AutoCAD crash.

I try to disable undo command, but if I set undo->control-none

everytime i run overkill, it give me this,means I have to set undo to 1. can't set it to none.

Thank you very much.