I totally missed out on the fact that my anti-viral program had expired and 'acquired' some malware in the time it took me to install MS Security Essentials.  However, since this time, I've had a couple of events which led me to suspect that damage had already been done - not least of which is the fact that I now can't log in to my Windows Live Mail or Messenger.  I simply get a message saying I can't be signed in because the service is 'temporarily unavailable' and an error code of 80070005.
   Trying to check this out as a bit of a dummy, I just find myself going round in circles and am worried that I may delete something meaningful in my efforts to repair it.  Can anyone help please?