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(Reuters) – Microsoft Corp issued its biggest-ever security fix on Tuesday, including repairs to its ubiquitous Windows operating system for flaws that could let hackers take control of a user’s personal computer.

Microsoft released 16 security patches to address 49 problems it identified in its products.

It said four of the patches were high priority and should be deployed immediately to protect users from potential criminal attacks on the Windows operating systems. The patches are software updates that write over glitches.

Microsoft said it also repaired other less serious security weaknesses in Windows, along with security problems in its widely used Office software for PCs and Microsoft Server software for business computers.

The total of 49 vulnerabilities exceeds the previous record of 34, which was set in October 2009 and matched in June and August of this year.

The constant patching of PCs is a time-consuming process for corporate users, who need to test the fixes before they deploy them to make sure they do not cause machines to crash because of compatibility problems with existing software.

(Reporting by Jim Finkle. Editing by Robert MacMillan)