from http://support.microsoft.com/Default.aspx?kbid=896054
Warning The MaxAllowedZone value enables all sites in a specific zone. Using UrlAllowList as described in example 1 may be safer. If you must use the MaxAllowedZone value, set it no higher than you must. If you set the value to 3 or higher, you expose your systems to attack from the Internet.
Note By default, the MaxAllowedZone value is set to zero. The following table summarizes how different entries are interpreted by the MaxAllowedZone value.
| MaxAllowedZone | Local Machine zone | Local intranet zone | Trusted sites zone | Internet zone | Restricted sites zone |
|---|---|---|---|---|---|
| 0 | Allowed | Blocked | Blocked | Blocked | Blocked |
| 1 | Allowed | Allowed | Blocked | Blocked | Blocked |
| 2 | Allowed | Allowed | Allowed | Blocked | Blocked |
| 3 | Allowed | Allowed | Allowed | Allowed | Blocked |
| 4 | Allowed | Allowed | Allowed | Allowed | Allowed |
The following .reg file re-enables use of the InfoTech protocol to connect to all systems in the Intranet zone.
REGEDIT4
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\HTMLHelp]
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\HTMLHelp\1.x\ItssRestrictions]
"MaxAllowedZone"=dword:00000001