(1) Install Arcv2CAD on your local drive.
(2) Copy the Arcv2CAD help file called arcv2cad4.chm to your local drive, and set the path to the new location of the help file in the [Help] section of Arcv2CAD ini file (A2C25.INI). For example if the help file was moved to c:\helpfiles the setting in A2C25.INI would be:
[Help]
HelpPath=C:\helpfiles\arcv2cad4.chm