is your activedirectory 200 or 2003 ?
if it is 2003 , then look up software restriction policies
The only problem with restricting access to IE is that it might well affect other parts of windows.
you'd be better of to restrict IE to only be able to connect to trusted sites , then use that trusted site list to maintain a whitelist of sites , which may well just be the company main site , or intranet.