Robert,

I'm assuming that you are actually talking about 'user profiles' and not
'user accounts' in the System Properties window found under the 'Profiles'
tab.  These 'unknown' user profiles are associated to previous local or
domain user accounts.  They can also be associated to current local accounts
that have become corrupted.  You should browse your profile directory at:

C:\Documents and Settings\%USERPROFILE%

TIP: Backup user profiles (folders) to another directory.

Each local user account will have a profile folder; provided the local user
has logged on--it gets created when the user first logs on.  If you delete a
user profile, it will delete the associated profile folder-just keep in mind
it doesn't delete the user account--accounts and profiles are two separate
things.  If you've got any more questions, just ask.

Best regards,

Todd

There appears to be multiple "unknown user" accounts on
my system. What are these and can I delete them?