We had a major one too recently. My DH had put both McAfee and Norton on the puter and apparently they are not compatible. DH got rid of McAfee and we don't have near the problems. We also have a spyware. Don't know which one.
DH was on the phone for four days with Dell and our server trying to get it fixed. He had more patience than I would have. I could not understand the techs. Anyway, be careful what you open. If you don't know who it is from, DELETE.