You might get a better response to your questions if you post in the Alienware Club forum. 
Go here and click the link under Warranty information to put in your Service Tag. It will tell you the warranty status.
Changing settings etc won't affect the warranty, assuming it hasn't expired. But if you installed some new hardware or replaced any factory hardware, Dell could ask you to put it back to "factory state" before they provide warranty assistance.
Hope somebody over there can help you get this sorted..