my laptop started to get slow a few days ago. when i started the laptop, it takes longer to load, longer to open firefox, and videos lag. i did a virus scan with avast and got rid of a few things. i also downloaded advanced system care and it showed i had a backdoor.frauder virus. i got rid of it and when i scanned it again, it would re-appear. how do i get of this? i also did a system restore, but it seems to appear again. i also downloaded hijackthis, but i don't understand any of the things that came up. can someone please help me with this?