I've never seen anything like this. I can't run a disc check or defrag. Everytime I start my computer windows explorer window pops up with a message saying that windows explorer has encountered a problem... If I try system restore the same message from restore pops up. system restore has encountered a problem... I cant delete any programs in add/remove programs it says windows installer cant be accessed or not installed correctly. I would greatly appreciate any help in this matter. I have Windows XP Home Version SP3 installed. I have CA installed for anti-virus. It is provided by Mediacom as part of their internet service.