never seen any of those windows alerts saying "system performance slowed down by........." etc, but then i guess thats because my pc hasnt been f'd up like that

Hmmm so did that site actually do anything then? your screenshot shows theres a virus but you didnt post a shot of anything positive?

Maybe another option is system restore to restore it back to the day when you didnt have this shit happening? maybe not work but worth a shot

If you do all of this and its still the same you might not have a choice but to reformat and start a fresh! do you have anything that you couldnt replace on this machine?