Dad's PC

Went to visit Mum & Dad last night, and Dad has a problem with his pc, can't remember his dsl username. So we find that, get him back online and his pc is running like a dog. Now it's not the fastest pc in the world anyway, but it normally runs better than this. Oddly his antivirus software has been turned up to maximum scanning - that'd do it everytime! Turned it back down to normal, and everything's coming up roses. Another technical hitch overcome.