Online shopping giant Tesco.com has migrated 2,000 desktops to Windows Vista with increased security and energy saving among the key reasons for the switch.
The retailer migrated the PCs to Vista Ultimate edition in January, following several months of testing.
Tesco.com IT and new technologies manager, Nick Lansley, explained there were three factors influencing the decision to move onto the new operating system.
A major consideration was security, of both customer information - such as payment details and addresses - and source code for the website.
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Lansley said: "It's really about our concerns for security - we wanted to have every base covered. Our source code is very important to us."
With company laptops often taken home by staff, Vista's network access protection tools were particularly useful according to Lansley. Vista's upgraded security features help make sure "nothing yucky" gets on the Tesco.com network, he said.
The group was also keen to get to grips with Vista to understand how Tesco.com customers using it might approach the site differently.
The final reason for switching was potential environmental benefits. Lansley said: "We wanted to see how much energy we could save."
Vista will detect if a computer is inactive and automatically switch to sleep mode, saving energy.
The PCs used by Tesco.com run at 300 watts when fully operational - but at just six watts in sleep mode.
Staff don't always think to put their PCs on standby but as Lansley said: "With Vista, it all comes naturally."
A more accurate picture of the power savings will be clearer following a technical audit of the 2,000 computers due to take place soon.
Tesco.com was part of the Vista early adopter programme, with testing starting in September last year, several months before its official launch.
Two people in each work team installed Vista to allow them to get used to its new features and understand any issues with the migration. After this testing period, full migration took place in the second week of January.
Although the rest of Tesco group remains on Windows XP, Tesco.com was able to complete the transition fast due to its smaller size - 400 people in a single building.