Utilities giant Centrica is migrating 26,500 staff from Microsoft Windows XP to Windows 7 in a desktop transformation set for completion by the end of 2013.
Desktop service provider Fujitsu will manage the £4m migration.
Centrica callcentre operations in 26 UK locations will be upgraded.
In April 2011,Centrica replaced T-Systems with Fujitsu as desktop service provider, as part of an IT outsourcing shake-up.
Centrica is planning to introduce new applications through the roll-out. It said many staff are already familiar with the operating system (OS), using Windows 7 at home or with previous employers.
The desktop transformation will also move Centrica closer to Windows 8, according to Fujitsu.
- Centrica names HP and Fujitsu in outsourcing reshuffle
- IT shops put off Windows XP migration to Windows 7, Windows 8
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Separately, data from ITSM supplier SysAid Technologies suggested that, up to April 2013, only 0.53% of enterprise computers running Windows OS were running on Windows 8.
By comparison, six months after the official launch of Windows 7, IT Benchmark indicated that 11.3% of enterprise computers running Windows OS were running Windows 7.