Head back to Best Buy and go through these steps.
1. Go to Customer Service and ask to see the "manager on duty" (MOD). That person is in fact responsible in full for the store at that time.
2. If the MOD cannot help you or refuses to help you, ask to speak to the store manager immediately.
3. If the store manager is not there (it happens, they have lives too) or cannot help you, demand the phone number and name of the store's regional manager, and make it crystal clear that you will spell out their names explicitly to the regional manager while you explain how unhappy you are with the service you've received.
4. At this point, there should be no way in hell that you're still stuck with the laptop. If by some extreme case this is not true, request the phone number to and talk to Corporate HQ for Best Buy as a final step.
They'll try to grind you out by all the threats and calls you may have to make, but if you escalate properly through these steps, once the manager(s) at the store hear you're willing to call their regional manager, they'll freak out and give you pretty much anything you want. Make sure to request "some compensation" for the time you've burned up in this mess (some $ on a gift card works).