Under the contract, Microsoft will supply a range of desktop and server software, including Windows XP, Microsoft Office XP and Windows 2000 Server.
It is the largest deal signed in Ireland by Microsoft since it introduced its controversial licensing system in 2001.
Cyril Dunne, chief information officer for BoI, said that Microsoft had proven to be a committed and flexible partner.
“We are pleased that we have reached an agreement,” he said.
Under the new licensing deal, customers pay Microsoft over several years rather than a one-time payment. This allows customers to access the latest software and upgrades as they are released.
Harry Largey of Microsoft said the company was committed to working with Bank of Ireland’s chosen outsourcing partner when that contract was awarded. He said the Bank of Ireland deal was the largest single enterprise contract ever won by Microsoft Ireland in the corporate sector.