I really don't hate Vista but it is problematic.
It has been my sad experience that many Vista installations do not stably
retain ownership/permission/sharing status from one session to the next.
This is true in Vista 32 and Vista 64. I'm sure some do, I have just never
seen one.
This is a given with external drives whose settings may be wiped out when
the unit powers down or is disconnected from the host machine. This behavior
is not a constant but a frequent occurrence.
It is an almost daily occurrence in my 2 small (5-10 machines) mixed
XP/Vista work environments that folders on a Vista machine, internal not
external hard drives, whose sharing/ownership settings have been correct and
have worked stably for some time suddenly no longer share properly. Not just
data folders but things like printers as well. Hence shared peripherals
should never be connected to a Vista machine if at all possible.
Drilling down through the obscure aracana of the sharing dialog boxes shows
that all settings are, indeed, correct and nothing has changed.
Microsoft and its apologists, who are the "MVPs" posting answers in this
newsgroup will deny this is so but it is a fact and one of many reasons why
Vista is unsuitable for large network environments. Who has the IT capacity
to constantly troubleshoot hundreds of unstable network clients? Or if the
client is to be locked down so hard that it is little more than a data input
terminal who needs the cost and overhead of Vista?
I hope that if you power down your drive, disconnect, reboot the machine and
reconnect the hard drive you will be able to reset permissions, at least for
that particular session. I most sincerely hope that you have never used any
password whatsoever.
If you can read the drive at all I would back-up any needed data to an
operating system neutral device like CD or DVD. That way if you have access
to an XP installation you may be able to retrieve the data and reset
attributes.