Microsoft is cutting the retail price of its Windows Vista operating system by as much as 20 per cent in the US, but will slash at least some versions' price tags by more than 46 per cent in both the UK and the European Union, the company confirmed Friday.

Late Thursday, Microsoft announced sweeping price cuts to boxed copies of Vista, saying then that the cuts would range from as low as 3 per cent in developed countries to nearly 50 per cent for some editions sold in poorer nations.

But by the numbers that Microsoft released Friday, even customers in Western Europe - France, Germany, Spain and the UK, among others - will also see prices fall by nearly half.

The price for the upgrade version of Vista Home Premium will drop 18.8 per cent in the US, from $159.95 to $129.95. The full edition of Vista Ultimate, on the other hand, will be cut 20 per cent, from $399.95 to $219.95.

But in the UK, Vista Home Premium upgrade will get chopped by 46.8 per cent, while the price of the full edition of Ultimate drops by 43.5 per cent.

Cuts in the European Union, said Microsoft, will be just as dramatic: the Home Premium upgrade will be slashed by 46.2 per cent, and the full version of Ultimate will be cut by 44.3 per cent. Some of the pound and euro amounts yanked off Vista's retail price are impressive: Ultimate sheds £101in the UK, and 165 Euros in the EU.

In other markets, such as India, some cuts are even deeper. The full version of Vista Home Basic will drop by 48 per cent. (In many markets, including India, Microsoft is combining the former full and upgrade packages into one SKU.)

Microsoft plans to institute the cuts when Vista Service Pack 1 (SP1) reaches retail. Earlier this month, the company announced it had shipped the SP1 code, and added that it would not deliver it to users via Windows Update for another six weeks. The company, however, has not set a specific retail date-of-availability.

"Retail customers will see boxed product with SP1 code on shelves in the next few months," said a Microsoft spokeswoman Friday.