XP: Prevent unauthorized website certificates from being able to install
Contributed by William_Wilson 
March 4, 2006 
Tagged: Windows networking
Prevent unauthorized website certificates from being able to install software onto your computers.
Most (myself not included) of us prefer to modify our computers and network with built in GUIs and Windows based fixes, instead of playing with the registry, so here’s a few tips using such a way.
Open Group Policy:
-go to start\run and type ‘gpedit.msc‘
-navigate to the path: local computer policy\computer configuration\administrative components\windows components\internet explorer\internet control panel\advanced page
-now double click the icon to the right called Allow software to run or install even if the signature is invalid
-select disable from the radio buttons
This will disable the ability to run OR install software from a website with an unwanted/unauthorized certificate. Preventing some of the headaches associated with multi-user networks and malicious scripts etc.
*NOTE this method only applies to the current computer, so this process either needs to be repeated on subsequent computers on the network, OR you must have the setting of your network updated from the current computer.
Questions/Comments: william_a_wilson@hotmail.com
-William. ยง (marvin_gohan)