Depends on what your looking to do. Processors that come Oem only have usually a 30 day warranty, but that is usually enough to tell if your chip is dead or not. Its very rare for a chip to fail if it has been working for 30 days with no problems. The retail chips on the other hand have a 3 year full warranty, and they come with the heat sink and fan, all the goodies. Cases dont matter, buy a quality case from a reputible company. I suggest onvia for free shipping, or buy.com, and buy will match prices on anything you find online. All other things its really up to you. I have never had a problem with oem ram, or hard drives, they usually carry the same warranty as retail. You dont get much more with a retail box with those items either. Video cards I can go either way, sometimes I like the nice box, and the bundled software. Drives are the same way, sometimes I want the cables that come with the drive. Motherboards I would go retail all the way so that you get everything that was supposed to come with it. That is my 2 cents, let me know what your looking for and I might be able to help you out.