Computer speed problem?

ok the other day i was just doin updates and my windows restarted and was on stage 2 of 2 and stayed there so i called samsung about the computer and they asked whats wrong i told them they said do a minor system restore so i would lose my stuff and what not well i did it it looked like my problem was fixed but then my firefox would cause my computer to blue screen with bad pool header and restart well i got tired of it so i went to the restore point befor i enstalled the updates and now im runnin pretty much fine but when im in wow now it seem like every few seconds i get like this screen lag it really fast like half a secong or less but it looks like it freezes and unfreeze really fast so you notinse it a lil when you turning and stuff but nothing to bad i was just wondering what would cause this and also if i should just restore my computer to factory and reinstall everything to make it faster if somthing got installed wrong or messed up while doin all that stuff they made me do.............oh yea i was also on netflix last night and tryied to watch a video and it didnt look that great liek it seemed like when the moves it would leave a lil pixel line behind thing like a shadow or somthing idl it did look right so im guessin it somthing to do with those updates messin somthing up but any help would be nice