StephenHowe,
Thanks for stopping by the Microsoft Surface community forum. We understand you would like to delete a user account on your Surface. Rest assured, we'll try and help.
I put together these step by step instructions that will help you achieve just that.
Please proceed as follow:
1 - Move the mouse cursor to the left corner of the start screen ( windows logo/Stat menu)
2 - Right click on the Windows logo(Also known as the start button)
3 - Click on Control Panel
The control Panel windows is now open.
4 - Click on " User Accounts and Family Safety"
5 - Click on " User Account"
6 - Click on " Manage Another account"
You are now presented here all account in Windows.
7 - Click on the account you would like to delete
In your case click on the gibberish account you would like to delete.
8 - Click on "Delete the account"
under Make changes to *********'s account (the gibberish account)
9- Click on "Delete Files"
if you'd like to delete all files associated with the account
10 - Click on "Delete account" to complete the process.
You've also mentioned that you'd like to create a new account howerver one that cannot create other accounts unless logged in as the administrator.
This is known as a limited account. Please click on this linkand follow the step by step instructions listed.
You can alternatively follow this great video tutorial to do just that as well.
Please let me know if that was helpful.
I look forward to your reply.