The BBC reports that the UK Home Office is talking to Microsoft over fears the new version of Windows could make it harder for police to read suspects' computer files.
Windows Vista is due to be rolled out later this year. Cambridge academic Ross Anderson told MPs it would mean more computer files being encrypted.
He urged the government to look at establishing "back door" ways of getting around encryptions.
A Microsoft spokeswoman said Windows Vista was designed to be the most secure version of Windows yet.
She said: "It is our goal to give PC users the control and confidence they need so they can continue to get the most out of their PCs.
"At the same time, we are working with law enforcement to help them understand its security features and will continue to partner with governments, law enforcement and industry to help make the internet a safer place to learn and communicate."
The system, part of what is called "trusted computing".
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