Bitsetting (AKA Booktyping) affects the disc, not your drive and there is no reason to think it will affect your warranty. You might be thinking of changing your firmware which might impact on your warranty, especially if something goes wrong during the flashing.
I provided some information in my earlier post using Nero and Kerry56 mentioned you could use the program imgburn. Hopefully, the screen shots will get you going.
By the way, Bitsetting is not a guarantee or a miracle cure but it does increase the possibility that your disc will play, especially on an older model.