Hello Jerry.
The basic underlying concept that is difficult for most of us to get our head around is that, if you log on to a Windows 7 Computer that has UAC (user account control) enabled, with an account that is a member of the local Administrator's Group, you get what Microsoft calls a "Filtered Access Token" as well as an "Administrator's Access Token". During normal operation your account then functions as a normal user account, except in those instances that may require elevated permissions in which case you get the annoying prompt to provide administrator credentials, in which case simply or normally clicking continue or OK will generally allow you to invoke your unfiltered access token and thereby support whatever action provoked the prompt for elevated credentials.
There is a lot of very confusing information regarding UAC and Filtered Access Tokens available if you want to use Google to do some research but as I said it's a bit confusing and muddled at best. Here is a relatively simple reference which may help you better understand what might be going on under the hood of Windows 7 regarding this topic.
SOURCE:
Programs may be unable to access some network locations after you turn on User Account Control in Windows Vista or in Windows 7
You seem to already know that you need to be careful regarding the handling of other accounts on your machine, and always make sure you preserve one administrator account. I might suggest using either an elevated command prompt and type
net user UserName /active:no (where UserName is the account you are wanting to deal with) to disable the account, or
net user UserName /active:yes (where Username is the account you are wanting to deal with) to enable the account
or by using the Local User Manager Console by typing
lusrmgr.msc
into the search or run dialog box to launch the console (if you are using Windows 7 Pro or higher)
and using the GUI to enable or disable accounts before deleting any accounts.