What is the reason for deleting these files?
These are your user profile files and generally shouldn't be deleted unless they have become corrupt. You can't delete them, because when you are logged into an NT operating system they are in use by the system. These do things like store your preferences for fonts, colors, desktop etc. They can be deleted, but be aware that all your user preferences will be gone. Windows wil regenerate these files for you, but they will be set to default.
Warning: Please read carefully:
You would have to log into the system as the administrator to delete the files of another user. If you are the administrator, then you have to create a new administrator user FIRST or you may find yourself locked out of your system as far as installing software or making any changes. Please do not attempt any of this without doing some reading FIRST and please remember to backup all your critical files and email before doing anything at all. If something goes bad, then at least you can reload windows from scratch and have all you critical docs available.
If you google these items (ntuser.dat etc), you'll find a wealth of information on how to manipulate them BUT PLEASE MAKE SURE YOU READ ALL THE INSTRUCTIONS BEFORE GOING AHEAD WITH ANY CHANGES.
Les