Microsoft Corp issued one of its biggest-ever security fixes on Tuesday, including repairs to its ubiquitous Windows operating system and Internet Explorer browser for flaws that could let hackers take control of a PC.

Microsoft said on Tuesday that two of the new patches -- software updates that write over glitches -- were of the highest priority and should be deployed immediately to protect users from potential criminal attacks on Windows and Internet Explorer.

The world's largest software maker 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 Exchange email software.

Altogether, Microsoft released 17 security patches to address 40 problems in its products.

The constant patching of PCs is time consuming 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 Andre Grenon)

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