Microsoft has apologised for the failure of servers managing data on Sidekick devices, and promised that most customers will get their data back by Saturday.

Roz Ho, Corporate Vice President Premium Mobile Experiences, Microsoft, apologises for problems and claims that "most, if not all" of the data has been recovered and will be restored to the servers over the next couple of days.

"I want to apologize for the recent problems with the Sidekick service and give you an update on the steps we have taken to resolve these problems,"she said.

"We are pleased to report that we have recovered most, if not all, customer data for those Sidekick customers whose data was affected by the recent outage. We plan to begin restoring users? personal data as soon as possible, starting with personal contacts, after we have validated the data and our restoration plan. We will then continue to work around the clock to restore data to all affected users, including calendar, notes, tasks, photographs and high scores, as quickly as possible," she added.

Users with affected Sidekick account should continue to log into the T-Mobile Sidekick forum at http://www.t-mobile.com/sidekick for the latest updates about when data restoration will begin, and any steps they may need to take.The next update on data restoration will be posted no later than Saturday, Microsoft said.

The company says that the outage was caused by a system failure that created data loss in the core database and the back-up.