As of Tuesday, more than 4,000 Brits had signed the petition, which in part reads: "We the undersigned petition the Prime Minister to bring pressure on Microsoft to stop them overcharging the U.K. for its Vista Operating System."
The petition appears on a site hosted by the office of U.K. Prime Minister Tony Blair.
On the site, the creator of the petition -- an individual named Paul Milne -- states that "I can see no reason for there to be such a huge difference in prices between the UK and the US other than Microsofts belief that the U.K. customers will pay more than their U.S. counterparts."
A price check Tuesday on Amazon.com's U.S. site showed that the upgrade version of Windows Vista is selling for $153.99. The same version is selling on Amazon's U.K. site for 129.48 GBP, or $254.53 in U.S. currency.
"I ask people to sign this petition in the hope that the Prime Minister will bring pressure to bear on Microsoft over their pricing as it is my belief they are simply overcharging the people of the UK and therefore are ripping us off," states Milne.
Microsoft officials were not immediately available to explain the pricing differential.