If your PC is registered and stolen it is registered to you the owner and it might help to get laptop back. Second it will make it easier to track maintenance of your machine. Dell for one has all the information on your pc and they notify you when new drivers come out.
Every laptop/PC I ever bought had to go through the horrible process of registering. Why is this necessary? Without registering, I was unable to go on-line. I found it impossible to skip the lengthy registration process. When first using an LCD TV or digital camera, registration can be skipped, so why PCs and laptops?

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