thats what i done a few times all prgrammes, pictrures,videos anything that i saved or loaded i put onto a external hdd. Then either get your recovery disk and set computer back to factory settings which will wipe everything and will be like new or google how to go into recovery mode for your comp type, its usually somthing like hit f12,f11,or f10 on start up and do it from there, once all wipe and fresh download avg and zonealarm the 2 i have found best so far and thats that. I have done this on sevral comps from guys from work and it really does make some diffrence cause antivirus programmes only prevent they dont completley delete a virus and if they find one they normaly put it in a vault which stays there cause usually its a part of a programme and if deleted the programme wont run, and that why it runs slow,or things take over when surfing the net