Reinstall OS X Mavericks
Just to clarify :-) Simply reinstalling an O/S (upgrading too) does not delete any personal files, it over writes only system files to a freshly installed state.

remember that the FIRST thing you do after re-installing is running software update and getting all the patches.

The SECOND would be booting from the recovery partition and repairing permissions and the disk with Disk Utility (in that order)