When starting ArcGIS Desktop Help from within ArcMap or ArcCatalog, the ArcGIS Desktop Help does not start, or the application crashes. ArcGIS Desktop Help does not start from the ArcGIS Desktop Help program group under the Start menu either.
Starting ArcGIS Desktop Help by double-clicking on C:\Program Files\ArcGIS\Help\ArcInfoMain.chm, the following error displays:
"Cannot open the file: mk:@MSITStore:C:\Program Files\ArcGIS\Help\ArcInfoMain.chm".
The Microsoft Help system may be corrupted.
Option 1: Follow the solution in the ESRI Knowledge Base article titled, "ArcMap help menu crashes", in the Related Information section below.
If the steps do not resolve the problem and/or the following error message is also displayed, then the Microsoft Help system may be corrupted and needs to be repaired.
Option 2: This problem may be caused by the hhctrl.ocx file in the System32 folder having been overwritten by an incompatible version. There is a link to an online forum titled, "'Cannot Open the File: Mk:@MSITStore' Error Message", describing this problem and how to fix it in the Related Information section below.
If replacing the hhcrtl.ocx file did not correct the problem, contact Microsoft Support.
Option 3: Some users have had success by running a repair on the Microsoft operating system. ESRI highly recommends contacting ESRI Support Services when selecting this option, as damage could occur to your operating system. ESRI cannot guarantee results from incorrect modifications. Therefore, use caution and proceed at your own risk.