In QuickBooks, reboot.bat is a batch file located in the QuickBooks program folder that re-registers .DLL and .OCX files under Microsoft Windows.
Repairing a QuickBooks installation also re-registers these files, along with performing other repair steps, so if you’re planning to repair your QuickBooks installation or if you’ve just completed that troubleshooting step, you don’t need to run reboot.bat.
Under Windows Vista, the default program folder for QuickBooks is:
C:Program FilesIntuitQuickBooks yyyy
where yyyy represents your version of QuickBooks, as in QuickBooks 2009.
Reboot.bat is also discussed in this Intuit knowledge base article, including additional information on locating batch file.