saralk's watchdog suggestion is a good idea.
You experienced your problem and got it "fixed" in your original warranty period. When the problem comes back within 2 weeks, even when using the restore CD and/or updated drivers, then that proves the problem wasn't fixed. The hardest part is that you need to have prove on when problems started and when/what was fixed etc.
I've worked on a computer shop for a half year and anwsering CS calls was part of it aswell. Hanging up on a customer is one of the worst things you can do, i know my ex-boss would wanna kill me if i did that
. If we had you as customer and your problem kept on exsisting after a full recovery and proper driver updates we would have taken it in, fixed and tested at no cost (if in warranty) and you get two months extra fix warranty + manufacture warranty on the replaced parts (most of the time a year).
So when you would have called back in 3 weeks after it was fixed we would have taken it in at once, test everything and make sure we fix it this time, even when your normal warranty is over, because you would have had the fix warranty, free of charge. If we can't fix it or problems come back every time, we would have replaced your PC with a new one of the same model or the model that comes closest to it. A happy customer is priority number one, because the customer is the person paying your loan
.
/ 
