To reset the tablet:
Determine which version you are running. For me it was .30WW
Go to www.asus.com and download the firmware for your version
plug your tablet into your usb on your computer, unzip the firmware and put it in the root of your tablet (Dont use USB or SD cards, just transfer it directly)
restart your tablet, it SHOULD load the file and go about resetting the tablet to stock.
If that does not work, try starting the tablet holding power and volume down, on the splash screen press volume up and reset the tablet that way.
Once your tablet is returned to stock you can proceed.
1) A contradiction (seemingly) that you say "plug your tablet into your usb on your computer" then "Dont use USB or SD cards"
That needs some clarification - if you plug into usb then you are using USB.
2) The above method doesn't work for me. By copying the file to the root of the tablet's sdcard I see two problems, a) Andy falls over - the error is that it can't find EP201_768_SDUPDATE.ZIP so by dropping the original filename this won't work without renaming. b) even if you rename it, it still complains because it's looking for it on the external sd card.
Unless I'm missing something I couldn't get your method to work. Also once I did rename it and put it on the external card, I still end up with a desktop full of my app shortcuts and data intact which implies either that this method doesn't clear data or it hasn't worked.
Would appreciate some clarification, I'm fully prepared to accept I've done something stupid but so far I've not been successful following the above.