Q:

Block user from opening IE

I have IE 6 on my family PC. Since I'm using Firefox, I don't intend to upgrade to IE 7. I'd like to  block anyone using IE 6 as it is not secure. How to do this. I have seen my cousins typing iexplore and opening IE though I have told them to use Firefox!

A:

Not upgrading to IE7 (or IE8 for that matter) still leaves you insecure even if you never use it.  There are many portions of windows that still use the IE rendering engine and system files that will remain vulnerable unless you upgrade.  There's also 3rd party software that uses the IE rendering engine.
Johannes's answer about adding the Deny flag to iexplore.exe might work for preventing people from running the full browser.  But don't delude yourself into thinking that makes you safe while you've still got the vulnerable IE6 core on the machine.

A:

You can change the permissions on iexplore.exe and remove the execute permission:

This can be found1 in the file's properties > Security > Advanced > Change permissions. There you have to uncheck "Include inheritable permissions from this object's parent" and then you can edit the permissions for the appropriate user.
The user will then get the following message box when attempting to run the program:

Ryan is correct, though. You really should upgrade the browser since it is a core component of Windows and can be exploited (or used in other applications) without explicitly running the browser. You may prevent this by keeping mshtml.dll from running, but I suspect this will cause much more harm than good.

1 The screenshots and instructions here work on Windows 7, however this should look nearly identical on XP or other legacy Windows versions.

A:

Change the proxy information for IExplorer so that it cannot connect to the Internet.  

Tools -> Internet Options -> LAN Settings -> Proxy Server

Set the proxy server to 127.0.0.1 and leave the Bypass check box empty.  
Doing this means that even if something else spans IE it will still not be able to connect to the Internet.  

