I just found how to unroot in post #140 by phonic in
http://forum.xda-developers.com/showthread...1287205&page=14"I don't think any of you understand what the 'rooting' process is here. This isn't some massive jailbreak like you have to do on an iCrap. Nor is it some lowlevel hack in the OS/firmware. All the 'root' script does is create a suid exec "su" program on the filesystem. It mounts the system filesystem as writeable, copies the file from the zip onto it, and remounts it non-writable. The reason for the extra step in booting into recovery mode is because, without the su command, you can't normally remount the system partition, nor write to it, nor give a program suid exec permissions (aka - giving it the ability to run as superuser or root).
That's it.
However, once the device is 'rooted', you can do all of those steps manually anyway because you now have root.
So if you want to unroot your tablet, you simply need to remove the 'su' binary. There are various ways to accomplish this, but one of the easier methods would be to download/install a terminal program, launch it, and issue the following commands:
su
mount -o remount,rw /system
rm /system/bin/su
umount -o remount,ro /system
exit
And voila, you have now unrooted your tablet. No need for a special zip package. If you have a file manager program that can utilize root access (not sure if there is one off the top of my head), you could use that to remove the file as well (assuming it can also remount /system with write access)."