Windows Installer appears when starting ArcMap

Error Message

When starting ArcMap, a Windows installer dialog box appears and attempts to install ArcGIS Desktop.

Cause

Some anti-virus programs, such as Trend Micro Office Scan, erroneously delete the file regobj.dll from the <system drive>:\windows\system32 or \winnt\system32 directory. This triggers the self-repairing feature of the ArcGIS installation to replace this file.

Note:
This file is NOT a virus; it is a required file which allows developers to access the registry from an ActiveX control.

Solution or Workaround

Do not let the anti-virus software delete this file; follow the steps below to prevent deletion.

Note:
If the problem persists after excluding and replacing the file, Trend Micro's Damage Cleanup Services may need to be updated. This is a known issue with the Trend Micro Office Scan product.  Please contact Trend Micro for the update. 

1. Add regobj.dll to the list of file exceptions so that the anti-virus program does not delete it. The procedure varies; contact the manufacturer of the anti-virus program for information on the procedure.
2. After excluding the file, run a repair of ArcGIS to replace the missing file:
   1. Insert the ArcGIS Desktop installation disk.
      • At 9.0 and 9.1, select Install ArcGIS Desktop.
      • At 9.2, click Exit, navigate to Start > Settings > Control Panel > Add or Remove Programs. Select ArcGIS Desktop and click the Change button.
   2. Select Repair and follow the prompts.