I had this same issue and tried all the above suggestions. What was causing my problem was the Task Scheduler service under Dependencies show WMI: not Found. I then checked the WMI service and it showed WMI: not found. I had to repair the WMI and that
fixed the Task Scheduler fixing the Office 2013 install problem. Here is the link to the WMI solution. I just had to do this part of the solution.
1. Log onto Windows 7 with an administrator account, click Start, type services.msc in the Start Search box and press Enter.
2. In the right pane of the Service console, locate and right-click Windows Management Instrumentation, and then select Stop to stop the
service.
3. Start Windows Explorer, and then locate the %SystemRoot%\System32\Wbem\Repository folder.
4. Backup and delete all the files in the %SystemRoot%\System32\Wbem\Repository folder.
5. Restart the computer.
The files that were deleted will be re-created when the computer restarts.
**Note:**The Windows Management Instrumentation service starts automatically when you restart the computer.
http://social.technet.microsoft.com/Forums/windows/en-US/1e1c9bec-425a-4b2c-a1db-ad1c92121806/wmi-failed-to-connect-to-local-computer-on-win-7-error-code-0x8007007e