just like the repair for any other item that was installed with windows insaller:
reviews any dll's , exe's or ocx's, as well as files for differences in the saved .msi and what is currently installled, and replaces them if they don't match/CRC doesn't match.;
i believe the isntaller alos looks at version numbers, so if something appears to have a higher version, (ie it was patched), it gets skipped.
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