Computer services in 80 NHS hospital trusts are down after an equipment failure on Sunday.
No patient data was lost because of the computer failure
Trusts in north-west England and the West Midlands were affected, said NHS Connecting for Health, which oversees the multi-billion pound NHS IT service.
The failure means staff cannot access patient administration systems, used to log admissions and transfers.
Systems should be restored on Monday evening. Until then, hospitals will have to log patient movements manually.
The problem affects trusts in Birmingham and the Black Country, Cheshire and Merseyside, Cumbria and Lancashire, Greater Manchester, Shropshire and Staffordshire and the southern part of the West Midlands.
The NHS Programme for IT aims to link more than 30,000 GPs to nearly 300 hospitals by 2014.
It is set to include an online booking system, a centralised medical records system for 50 million patients, e-prescriptions and fast computer network links between NHS bodies.
A spokesman for NHS Connecting for Health said the system did not hold clinical information.
He confirmed there had "regrettably" been "serious interruption to computer services".
"This incident was caused by storage area network equipment failure and has affected several other organisations," he said.
"Technical issues following power system interruptions mean that data held on computers in the central data centre for the region cannot be accessed.
"The nature of the incident meant that service could not immediately be provided by the back-up systems.
"No data has been lost."
He said trusts could register patient movements using a paper system, but that it was more "time-consuming and cumbersome".
Experts from CSC Alliance, the company which manages the systems, and its sub-contractor Hitachi have been "working round the clock to restore access to data", he added.
Adrian McDermott, deputy chief information officer for NHS North West, said the computer problem meant medical staff had not been able to check hospital appointments on screen, but were having to do the work manually, through lists on paper.
About 2,000 patients in Greater Manchester had been affected, but hospitals and clinics had contingency plans in place to deal with the problem.
Mr McDermott said the system crash had not resulted in any medical emergencies and it had not affected the computer system that allows doctors to look up the medical records of patients.
He added: "We have managed the impact as best we can."
A spokeswoman from the Department of Health said: "It is regrettable that the issue in the North West and West Midlands is causing inconvenience to patients.
"However, the affected NHS trusts have back-up systems to ensure they can continue with their day-to-day business.
"NHS Connecting for Health is working quickly with the supplier of the
computer system to resolve this issue as quickly as possible."
Shadow Health Minister, Stephen O'Brien, said: "Despite the huge amounts of tax payers' money which has been sprayed at the NHS IT system, it continues to be left wanting."