Hi
A final update on my problem: After successfully editing the registery and removing the offending item I am now fully operational again and able to open .pdf files in IE6 ok.
Sparkie,
Sorry to see that you have'nt received any suggestions re your problem. Might I suggest that you go to microsoft .com and then look for "community newsgroups". In there are lots of different discussion groups ( I posted in the IE6 section) with lots of expertise on everything concerning windows. It was there I eventually got sorted.
Thanks to all who replied , your assistance was appreciated.
Willby