Take it back to Best Buy, tell them that you're unsatisfied with the job they did, explain why, and then demand that they fix it.
Next time, I'd avoid using Geek Squad or any other similar service. You probably have no more than a 50/50 chance of someone who has even half a clue working on your system. Look around your area for computer shops, and start asking around to see how reputable they are.
Sadly, kind of like the auto repair industry, computer repair shops can sometimes be very shady. Many will install pirated software, swap out expensive components for cheaper ones, suggest repairs that are unnecessary, etc. At least one good indicator of a place to avoid, is asking if they have any problem with you being present for any and all work to be done. If they have no problems with that, it's a good sign, though it doesn't mean everything they do is above board.
If there are no local shops, or shops within a reasonable driving distance, ask friends and neighbors if maybe any of them have a kid or relative who's good with that sort of thing and might be willing to help. Odds of success are probably about as good as using a service like Geek Squad this way, but it's probably cheaper and you're helping some local kid instead of a large faceless corporation.
That's my suggestion anyway. Feel free to take it or ignore it.
Ever since i got my computer back from Geek Squad, it seems like theres more problems now than there was before i gave it to them. I got it back without a MPEG-2 codec thing and so i bought one, so that i can watch DVD's. now I have no idea if that codec is affecting this, but I CANT WATCH AVI OR m4v FILES! Like when i watch AVI, if i resize the screen is spaz lags out making a GEGEGEGEGEGEGEGEGEG noise lol. and m4v's, when i play them, they just flat out dont play. its a bunch of squares and lines and that same GEGEGEGEGEG noise. now i have this problem on windows media player, and quicktime pro. Aaand Yes ive reinstalled both programs, and yeees i've reinstalled my video drivers and sound drivers. now this is where no one can seem to figure it out.
PLEASE HELP IF YOU CAN!