Administrator has lost it's Priviledges

[Guest]

Using Windows XP Professional with Service Pack and logged in as Computer
Administrator I find that I have lost administrator privileges.
Right Mouse for Properties on folder 'Documents and Settings' or 'All Users'
now no longer works.
When I attempt to install a new applications I get the error message 'You do
not have necessary privileges, login as administrator or contact your system
administrator'.
I have checked Security Setting for Drive C: and found setting for
administrator to be correct i.e. ticks in all boxes.
I have reapplied permissions 'to object and/or within this container only',
'replaced permission entries on all child objects with entries shown here
that apply to child objects' and removed simple sharing and removed sharing
of the C: Drive.
The problem still persists.

Any Ideas?

 

[Guest]

I've got the same problem on 2 of 3 administrator accounts, including the
built-in. It's keeping me fom installing some programs and setting Sun Java
as the default in IE. Any suggestions anyone?