changing regional settings to play multi regional dvds

hi all
Ive just bought one of those new philips home packages which is running
vista home premium. I have many dvds from america and canada as well as from
the uk, i am nearly bald after trying for 4 days to try and change the
regional settings, on my old computer (which ran xp home premium) i had no
trouble at all, this is now really getting silly can someone please help me
when i try i get the message you must change the regional settings to 1 or 4
when i try this i get the message unable to do this speak to the
administrator .... I am the administrator. anyone have any clue? all help
gratefully accepted.
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many thanks lesley