Internet Explorer 6 crashes when visiting certain sites

I am trying to help a friend clear up a very annoying problem with
IE6 on his Windows XP Home machine.
Originally the problem was that when my friend surfed the net, many times graphics, pictures or buttons would not display-instead he would see a white box with a red x. I thought it might be an encoding issue and found that whenever I changed the encoding back to unicode, the page would display normally. We would try a few more pages then we would see the red x again. I checked encoding and it had changed from unicode to one of the western European codes (it varied). We tried auto-select with no luck either.
Some of the pages will display ok with the European (Windows or ISO) code selected, others won't. We tried Windows UPDATE but there were no critical updates available. I tried reinstalling IE6 but the set up fails-the installer says that we already have a newer version (than the one we are trying to load. After a couple of reboots the red x problem has been replaced by IE crashing.If we visit a page and IE crashes (with the box stating that "Internet Explorer has encountered a problem and needs to close. " etc.)
we find that if we check the encoding it is not unicode but one of the
West European codes. We then click on the send error report to Microsoft and IE closes. I can find nothing helpful on the Microsoft Knowledge Base pages. We found a possible solution on another forum that suggested editing the registry key: HKEY_LOCAL_MACHINES\SYSTEM\CurrentControlSet\Nls\CodePage
and setting the default to C_28591.NLS but that did not work for us. We undid the edit. (There were suggestions to set all of the lines in that key to C_28591.NLS but did not try that.

Any help would be greatly appreciated.