There are detailed step by step instructions on how to disable ICS in the link I listed above (that you for some reason rejected). Here they are again:
Disabling ICS
There are three ways you can disable ICS: through the Desktop, through the Control Panel, or through editing the Registry.
Desktop
To disable ICS through the Desktop, use the following steps.
Right Click on My Computer and select Manage > Services and Applications.
Select Services > Internet Connection Sharing located under ICS Firewall.
Disable Load on Startup. IPSec is also found under Services.
Control Panel
To disable ICS through the Control Panel, use the following steps.
Got to Start > Settings > Control Panel > Administrative Tools > Services.
Select Services > Internet Connection Sharing located under ICS Firewall.
Disable Load on Startup. IPSec is also found under Services.
If the above does not work, then try editing the registry. It is possible that even though the Control Panel shows ICS as disabled, the registry value could still show it as enabled. In that case you still need to disable ICS through the registry even though you already disabled it through the Control Panel.
Registry
To disable ICS through the Registry, use the following steps.
Test the regkey for the existence of ICS on Windows XP by doing the following:
Go to Start > Run and type regedit.
Click OK.
In the Registry Editor, double-click on HKEY_LOCAL_MACHINE | SYSTEM | CurrentControlSet | Services | SharedAccess.
Now review the DWORD value Start, where 0x2 = ICS enabled and 0x3 = ICS disabled. If the value shows 0x2, then right click and modify it to show 0x3. This will manually force ICS to shut off and allow the VPNClient installation to continue.