Sometimes I find the easiest way is to edit the registry. [Use regmon.]
The key your looking for is
[HKEY_CURRENT_USER\Software\Adobe\Acrobat Reader\8.0\Originals]
"bBrowserIntegration"=dword:00000000
so create
WshShell.RegWrite "HKEY_CURRENT_USER\Software\Adobe\Acrobat Reader\8.0\Originals\bBrowserIntegration", 0, "REG_DWORD