Help: Rooted tablet but can't delete file in /system no matter what I do.

I rooted my strange tablet using Kingo and apparently it was succesful:
http://i1312.photobucket.com/albums/...psurdgzj8p.png

But I have been trying for days to erase a file in /system and I have not been able to do it, I think I have read every relevant thread about this problem but no luck, I tried using ES and changed /system to r/w in the root options but when trying to delete the file all I get is operation failed, the same happens with all the other root explorers and tools. I even tried the solution on this thread: http://forum.xda-developers.com/asce...table-t2884172
but still can't delete it.

Also the app root toolkit for android gives me this weird error too:
http://i1312.photobucket.com/albums/...ps4nrxqiev.png
http://i1312.photobucket.com/albums/...psa1ycwdwl.png