Thanks for the advice and link but having read it all I'm really none the wiser. The only remaining issue is the message "Error loading iSecurity.cpl. etc." which keeps popping up. It would be nice to know what it means, and how the cause can be eliminated.
"iSecurity.cpl" is linked to spyware - HOWEVER, it isn't on your pc anymore (hence the message).
You still have some entries in the system registry which are trying to load it and because it isn't there, you get the message.
If you are not a geeky person, I wouldn't recommend messing with the registry - even Microsoft can cock it up!
I can recommend this tool:
Bazooka, which will find all the hidden nasties and
may help you get rid of them. Otherwise, a registry cleaner, like Ccleaner is next best BUT keep a before-copy of your registry, just in case.