Sometimes you need to make the DVD region free first using a firmware update. Then fool windows by using software such as DVD REgion Killer click here I assume if you did it in the past you have already updated the drives firmware, so just try the software.
Thanks for all the info. Great links too. Should be sorted now. (I should have mentioned that the manufacturer that originally told me how to do this was Gateway - which surreptitiously slunk back into its lair on the other side of the pond, overcome by a beast even more vile than capitalist meglamania: Europe.)
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